--- title: "Redis" lang: "en" author: "Mohammad Abu Mattar" canonical: https://mkabumattar.com/redis --- 0 [Home](/)›[Cheatsheets](/cheatsheets) Cheatsheets # Redis Redis reference guide covering commands, data types, keys, strings, lists, sets, hashes, sorted sets, transactions, pub/sub, and caching strategies. 10 Categories32 Sections145 ExamplesPublished: 28 Feb 2026 [Markdown for AI(opens in a new tab)](/redis/index.md "Open the plain-Markdown version of this page, for pasting into an AI tool") Series [Databases & Data Persistence](/series/databases--data-persistence)2/2 [PreviousPostgreSQL](/cheatsheets/postgresql) All posts in this series (2) Cheatsheets2 1. [PostgreSQL](/cheatsheets/postgresql) 2. [RedisYou are here](/cheatsheets/redis) Redis reference guide covering commands, data types, keys, strings, lists, sets, hashes, sorted sets, transactions, pub/sub, and caching strategies. [Getting Started](#category-getting-started) - [Redis CLI Basics](#section-redis-cli-basics) - [INFO Command and Server Stats](#section-info-command) - [Configuration Commands](#section-configuration-commands) - [Connection Pooling Concepts](#section-connection-pooling) [Keys Management](#category-keys-management) - [Key Deletion and Existence](#section-key-deletion-existence) - [Key Expiration and TTL](#section-key-expiration-ttl) - [Key Scanning and Enumeration](#section-key-scanning) - [Key Type Checking and Operations](#section-key-type-operations) - [Key Renaming and Moving](#section-key-renaming) [String Operations](#category-strings) - [String Get and Set Operations](#section-string-get-set) - [String Manipulation Commands](#section-string-manipulation) - [String Numeric Operations](#section-string-numeric-operations) - [String Bit Operations](#section-string-bit-operations) [List Operations](#category-lists) - [List Push and Pop Operations](#section-list-push-pop) - [List Range Operations](#section-list-range-operations) - [List Blocking Operations](#section-list-blocking-operations) [Set Operations](#category-sets) - [Set Add and Remove Operations](#section-set-add-remove) - [Set Operations (Union, Intersection, Difference)](#section-set-operations) - [Set Advanced Operations](#section-set-advanced) [Hash Operations](#category-hashes) - [Hash Get and Set Operations](#section-hash-get-set) - [Hash Numeric Operations](#section-hash-numeric-operations) - [Hash Scanning and Enumeration](#section-hash-scan) [Sorted Sets Operations](#category-sorted-sets) - [Sorted Set Add and Remove Operations](#section-sorted-set-add-remove) - [Sorted Set Range Queries](#section-sorted-set-range-query) - [Sorted Set Increment Operations](#section-sorted-set-increment) [Transactions & Scripting](#category-transactions-scripting) - [Transaction Basics](#section-transactions-basics) - [Lua Scripting](#section-lua-scripting) [Pub/Sub & Streams](#category-pubsub-streams) - [Pub/Sub Basics](#section-pubsub-basics) - [Redis Streams](#section-redis-streams) [Advanced Features](#category-advanced-features) - [Persistence (RDB and AOF)](#section-persistence-rdb-aof) - [Replication and Clustering](#section-replication-cluster) - [Memory Optimization](#section-memory-optimization) No commands found Try adjusting your search term ## Getting Started ### Redis CLI Basics Connect and interact with Redis using redis-cli command-line tool #### Accessibility Beginner #### Best Practices - Always authenticate when connecting to production servers - Use connection pooling in applications - Specify explicit port and host for clarity - Use SELECT carefully in scripts to avoid database number mistakes #### Common Errors - **Connection refused:** Start the Redis server, or correct the host and port - **Authentication required:** Wrong or missing password with -a flag - **Database index out of range:** Valid indices are 0-15 for default config #### Keywords redis-cliconnectionauthenticationselect database [Learn more](https://redis.io/commands/docs/) #### Connect to Local Redis Default Opens interactive Redis CLI session on localhost port 6379 Code Terminal window ``` redis-cli ``` Execution ``` 1127.0.0.1:6379> ``` - Default Redis server runs on port 6379 - Requires Redis server to be running - Ctrl+C to exit the CLI #### Connect to Remote Redis Server Connect to Redis on host redis.example.com with port 6380 and password authentication Code Terminal window ``` redis-cli -h redis.example.com -p 6380 -a yourpassword ``` Execution ``` 1redis.example.com:6380> ``` - \-h specifies hostname or IP address - \-p specifies custom port - \-a provides password authentication #### Execute Command from Command Line Execute a single command without entering interactive mode Code Terminal window ``` redis-cli PING ``` Execution ``` 1PONG ``` - Useful for scripts and automation - Returns result to stdout #### Select Database Index Switch to database 1 (Redis has 16 databases by default, indexed 0-15) Code Terminal window ``` redis-cli127.0.0.1:6379> SELECT 1 ``` Execution ``` 1OK2127.0.0.1:6379[1]> ``` - Each database has separate keyspace - Default is database 0 - Useful for testing without affecting production data ### INFO Command and Server Stats Retrieve detailed Redis server information and statistics #### Accessibility Beginner #### Best Practices - Monitor memory usage regularly to avoid eviction - Check maxmemory policy matches your use case - Use specific sections when integrating with monitoring tools - Track connected\_clients to detect connection leaks #### Common Errors - **Wrong number of arguments:** Use INFO section\_name for specific info - **Parsing INFO output:** Numbers are strings in bash, cast to int if needed #### Keywords INFOserver statisticsmemory usageconnected clients [Learn more](https://redis.io/commands/info/) #### Get All Server Information Displays all available server information across all sections Code Terminal window ``` redis-cli INFO ``` Execution ``` 1# Server2redis_version:7.0.03redis_mode:standalone4os:Linux 5.15.0 x86_645arch_bits:646uptime_in_seconds:34567uptime_in_days:08# Clients9connected_clients:4210blocked_clients:011# Memory12used_memory:104857613used_memory_human:1.00M14maxmemory:015# Stats16total_connections_received:15617total_commands_processed:8923 ``` - Output is formatted in sections starting with - Large output on busy servers - Shows uptime, client count, memory usage, commands processed #### Get Specific Section Only Retrieve memory statistics only (more targeted than INFO all) Code Terminal window ``` redis-cli INFO memory ``` Execution ``` 1# Memory2used_memory:20971523used_memory_human:2.00M4used_memory_rss:41943045maxmemory:10737418246maxmemory_human:1.00G7maxmemory_policy:noeviction ``` - Available sections: server, clients, memory, persistence, stats, replication, cpu, cluster, modules - Useful for monitoring specific metrics #### Check Connected Clients and Commands Monitor requests per second and total throughput metrics Code Terminal window ``` redis-cli INFO stats ``` Execution ``` 1# Stats2total_connections_received:5233total_commands_processed:125434instantaneous_ops_per_sec:455evicted_keys:3 ``` - ops\_per\_sec shows current command rate - evicted\_keys indicates memory pressure - Useful for performance monitoring ### Configuration Commands View and modify Redis server configuration at runtime #### Accessibility Intermediate #### Best Practices - Test configuration changes on non-production first - Always rewrite config after runtime changes you want to keep - Set maxmemory-policy based on use case (volatile-lru for caching) - Monitor memory with CONFIG GET to prevent OOM errors #### Common Errors - **ERR Unknown CONFIG subcommand:** Check spelling of parameter name - **Config value out of range:** Use a value inside the valid range #### Keywords CONFIG GETCONFIG SETruntime configurationpersistence settings [Learn more](https://redis.io/commands/config-get/) #### Get Configuration Value Retrieve current value of maxmemory configuration parameter Code Terminal window ``` redis-cli CONFIG GET maxmemory ``` Execution ``` 11) "maxmemory"22) "1073741824" ``` - Returns array with parameter name and value - Value is in bytes #### Get Multiple Configuration Parameters Use wildcard patterns to retrieve related parameters Code Terminal window ``` redis-cli CONFIG GET "max*" ``` Execution ``` 11) "maxmemory"22) "1073741824"33) "maxmemory-policy"44) "noeviction" ``` - Supports glob patterns like max\*, \*memory\* - Useful for exploring configuration space #### Set Configuration Value Change maxmemory to 2GB at runtime without restart Code Terminal window ``` redis-cli CONFIG SET maxmemory 2147483648 ``` Execution ``` 1OK ``` - Not all parameters can be changed at runtime - Changes persist only during session unless saved to config file #### Rewrite Configuration to File Save all runtime configuration changes to the config file Code Terminal window ``` redis-cli CONFIG REWRITE ``` Execution ``` 1OK ``` - Preserves comments and structure of original file - Makes runtime changes permanent ### Connection Pooling Concepts Managing Redis client connections and connection pools #### Accessibility Intermediate #### Best Practices - Use connection pooling in applications (min 5, max 20 connections) - Monitor connected\_clients in production - Set reasonable PING intervals in pools to detect dead connections - Use CLIENT SETNAME to identify connection sources in logs #### Common Errors - **Too many connections:** Increase maxclients or fix connection leak in code - **Connection reset by peer:** Check network stability and firewall rules #### Keywords connection poolingpersistent connectionsclient listHELLO protocol [Learn more](https://redis.io/commands/client-list/) #### List All Connected Clients Display list of all clients connected to Redis server Code Terminal window ``` redis-cli CLIENT LIST ``` Execution ``` 1id=1 addr=127.0.0.1:45678 fd=8 name= age=15 idle=0 flags=N db=0 sub=0 psub=0 multi=-12id=2 addr=127.0.0.1:45679 fd=9 name= age=2 idle=1 flags=N db=0 sub=0 psub=0 multi=-1 ``` - Each line represents one client connection - idle shows seconds since last command - flags: N=normal, d=dirty, R=readonly, etc. #### Get Client Connection Count Quick way to check current number of connected clients Code Terminal window ``` redis-cli INFO clients | grep connected_clients ``` Execution ``` 1connected_clients:8 ``` - Monitor this metric to detect connection leaks - Compare with maxclients setting #### Kill Idle Client Connection Terminate specific client connection by address Code Terminal window ``` redis-cli CLIENT KILL 127.0.0.1:45678 ``` Execution ``` 1OK ``` - Useful for removing stuck or idle connections - Client will reconnect if pool is configured #### Set Client Name for Tracking Assign name to current connection for monitoring purposes Code Terminal window ``` redis-cli CLIENT SETNAME "app-worker-1" ``` Execution ``` 1OK ``` - Visible in CLIENT LIST output - Helpful for debugging multiple connections ## Keys Management ### Key Deletion and Existence Check existence and delete keys from Redis database #### Accessibility Beginner #### Best Practices - Use UNLINK for large keys to avoid blocking - Check EXISTS before expensive operations - Batch deletes with multiple keys to cut round trips - Be cautious with DEL on patterns (use SCAN+DEL instead) #### Common Errors - **Key not found errors:** DEL returns 0 for non-existent keys, not an error - **Using DEL with patterns:** Use SCAN+DEL, pattern matching not supported #### Keywords DELEXISTSUNLINKkey deletion [Learn more](https://redis.io/commands/del/) #### Delete Single Key Create and delete a key, DEL returns number of keys deleted Code Terminal window ``` redis-cli SET mykey "Hello"redis-cli DEL mykey ``` Execution ``` 1OK2(integer) 1 ``` - Returns the count of keys actually deleted - Returns 0 if key doesn't exist - Synchronous operation #### Delete Multiple Keys Delete multiple keys in one command, returns total deleted count Code Terminal window ``` redis-cli DEL user:1 user:2 user:3 session:abc ``` Execution ``` 1(integer) 4 ``` - More efficient than multiple DEL commands - Atomic operation, deletes all or none #### Check If Key Exists Returns 1 if key exists, 0 if it doesn't Code Terminal window ``` redis-cli EXISTS mykey ``` Execution ``` 1(integer) 1 ``` - Fast O(1) operation - Can check multiple keys, returns sum of existing keys #### Check Multiple Keys for Existence Returns count of how many keys exist among the given ones Code Terminal window ``` redis-cli EXISTS user:1 user:2 user:3 nonexistent ``` Execution ``` 1(integer) 3 ``` - Useful for batch existence checks #### Asynchronous Key Deletion Non-blocking deletion, especially useful for large keys Code Terminal window ``` redis-cli UNLINK large_list large_hash large_set ``` Execution ``` 1(integer) 3 ``` - Faster than DEL for large data structures - Deletes in background thread - Same return value as DEL ### Key Expiration and TTL Set and manage key expiration times #### Accessibility Beginner #### Best Practices - Always set expiration on temporary data (sessions, OTPs, cache) - Use appropriate TTL: sessions 1-24 hours, OTP 5-15 minutes, cache based on freshness - Monitor expired keys with CONFIG GET "lazyfree-lazy-eviction" - Set slightly longer TTL than needed to avoid premature expiration #### Common Errors - **Key immediately disappears:** Check TTL immediately after setting - **TTL returns -2:** Key was already expired and removed - **Too short TTL:** Users see errors when key expires during their session #### Keywords EXPIRETTLEXPIREATPEXPIREpersistence settings [Learn more](https://redis.io/commands/expire/) #### Set Key Expiration in Seconds Set key to expire in 3600 seconds (1 hour) Code Terminal window ``` redis-cli SET session:token "abc123xyz"redis-cli EXPIRE session:token 3600 ``` Execution ``` 1OK2(integer) 1 ``` - Returns 1 if timeout set, 0 if key doesn't exist - Session keys typically use EXPIRE #### Check Remaining Time To Live Returns seconds remaining until key expires Code Terminal window ``` redis-cli TTL session:token ``` Execution ``` 1(integer) 3598 ``` - Returns -1 if key exists but has no expiration - Returns -2 if key doesn't exist - Use PTTL for millisecond precision #### Set Millisecond Expiration Set key to expire in exactly 5000 milliseconds (5 seconds) Code Terminal window ``` redis-cli PEXPIRE rate-limit:user123 5000 ``` Execution ``` 1(integer) 1 ``` - Useful for rate limiting and short-lived data - PTTL returns milliseconds remaining #### Set Expiration at Unix Timestamp Set key to expire at specific Unix timestamp (Jan 1, 2024) Code Terminal window ``` redis-cli EXPIREAT cache:data 1704067200 ``` Execution ``` 1(integer) 1 ``` - timestamp is in seconds since Unix epoch - Useful when you know exact expiration time #### Remove Key Expiration Remove expiration from key, making it permanent Code Terminal window ``` redis-cli PERSIST session:token ``` Execution ``` 1(integer) 1 ``` - Returns 1 if timeout removed, 0 if already permanent or doesn't exist #### Set Value with Expiration in One Command Set key with value and 300-second expiration in single command Code Terminal window ``` redis-cli SET otp:email@example.com "654321" EX 300 ``` Execution ``` 1OK ``` - EX = expire in seconds, PX = expire in milliseconds - More efficient than SET followed by EXPIRE - NX/XX options work with EX/PX ### Key Scanning and Enumeration Iterate through keys without blocking Redis server #### Accessibility Intermediate #### Best Practices - Always use SCAN for large datasets, never use KEYS pattern - Handle cursor=0 as end condition in loops - Use MATCH pattern to filter results server-side - Implement timeout to prevent infinite loops #### Common Errors - **Using KEYS pattern in production:** Blocks entire server, use SCAN instead - **Infinite loops:** Forget to increment cursor or return to 0 - **No results:** Add COUNT higher or check pattern matches existing keys #### Keywords SCANpattern matchingcursor iterationnon-blocking enumeration [Learn more](https://redis.io/commands/scan/) #### Scan All Keys with Cursor Start scanning from cursor 0, returns next cursor and matching keys Code Terminal window ``` redis-cli SCAN 0 ``` Execution ``` 11) "2048"22) 1) "user:profile:123"3 2) "session:token:abc"4 3) "cache:homepage" ``` - Returns \[next\_cursor, \[keys\]\] - Continue with cursor 2048 to get more keys - O(1) per iteration, doesn't block server #### Scan with Pattern Match Scan only keys matching "user:\*" pattern Code Terminal window ``` redis-cli SCAN 0 MATCH "user:*" ``` Execution ``` 11) "1024"22) 1) "user:profile:1"3 2) "user:profile:2"4 3) "user:settings:100" ``` - Pattern matching happens on server side - Still uses cursor iteration, not all-at-once retrieval #### Scan with Count Hint Return approximately 100 keys per iteration Code Terminal window ``` redis-cli SCAN 0 COUNT 100 ``` Execution ``` 11) "512"22) 1) "cache:data:1"3 2) "cache:data:2"4 3) "cache:data:3" ``` - COUNT is hint, not strict count - Larger COUNT may return many keys - Useful for batch operations #### Complete Scan Iteration in Bash Loop through all keys matching pattern until cursor returns to 0 Code Terminal window ``` cursor=0while true; do result=$(redis-cli SCAN $cursor MATCH "session:*" COUNT 50) cursor=$(echo "$result" | head -1) echo "$result" | tail -1 [[ $cursor -eq 0 ]] && breakdone ``` Execution ``` 1session:user12session:user23session:user34[... more sessions ...] ``` - Proper way to enumerate all keys when using SCAN - Safe for production use #### Scan Hash Fields Scan fields of hash without loading all fields at once Code Terminal window ``` redis-cli HSCAN user:1:profile 0 ``` Execution ``` 11) "0"22) 1) "name"3 2) "John Doe"4 3) "email"5 4) "john@example.com" ``` - Works similarly to SCAN with cursor-based iteration - Also available as SSCAN for sets, ZSCAN for sorted sets ### Key Type Checking and Operations Determine and manipulate key data types #### Accessibility Intermediate #### Best Practices - Check TYPE before operations that expect specific data type - Use DUMP/RESTORE for backup or cross-instance migration - Monitor MEMORY USAGE for large keys - Document your key naming conventions for type inference #### Common Errors - **WRONGTYPE operation:** Wrong operation for key type (e.g., LPUSH on string) - **DUMP not matching between versions:** Different Redis versions may serialize differently #### Keywords TYPEDUMPRESTORECOPYMIGRATE [Learn more](https://redis.io/commands/type/) #### Check Key Data Type Returns the data type of specified key Code Terminal window ``` redis-cli SET mystring "hello"redis-cli LPUSH mylist "item1"redis-cli TYPE mystringredis-cli TYPE mylist ``` Execution ``` 1OK2(integer) 13string4list ``` - Returns: string, list, set, zset, hash, stream - Returns "none" for non-existent keys #### Dump and Restore Key Serialize key content for backup or transfer Code Terminal window ``` redis-cli SET backup-key "important data"redis-cli DUMP backup-key ``` Execution ``` 1OK2"\x00\x10important data\x09\x00\x8f\xf6\x8f\xf6\x00\x00\x00\x00" ``` - Returns serialized value in Redis protocol format - Can be restored with RESTORE command in different instance #### Copy Key to New Name Create copy of key with new name Code Terminal window ``` redis-cli SET original-key "data"redis-cli COPY original-key backup-key ``` Execution ``` 1OK2(integer) 1 ``` - Returns 1 on success, 0 if destination already exists - Use REPLACE option to overwrite destination #### Get Key Memory Usage Returns memory consumption of key in bytes Code Terminal window ``` redis-cli MEMORY USAGE mykey ``` Execution ``` 1(integer) 56 ``` - Includes Redis internal overhead - Useful for finding keys that consume the most memory ### Key Renaming and Moving Rename keys or move them to different databases #### Accessibility Intermediate #### Best Practices - Use RENAMENX for safe renames to prevent data loss - Separate concerns by database when appropriate - Plan key naming conventions to minimize renaming - Consider key migration strategy for growing applications #### Common Errors - **ERR no such key:** Source key doesn't exist - **Destination already exists:** Use RENAMENX to check first #### Keywords RENAMERENAMENXMOVEatomic operations [Learn more](https://redis.io/commands/rename/) #### Rename Key Rename key atomically, old key is replaced with new name Code Terminal window ``` redis-cli SET old-name "content"redis-cli RENAME old-name new-nameredis-cli GET new-name ``` Execution ``` 1OK2OK3"content" ``` - Returns error if source key doesn't exist - Overwrites destination key if it exists #### Rename Only If New Name Doesn't Exist Rename only if destination key doesn't already exist Code Terminal window ``` redis-cli RENAMENX temp-data permanent-data ``` Execution ``` 1(integer) 1 ``` - Returns 1 if renamed, 0 if destination exists - Useful for conditional renames #### Move Key to Different Database Atomically move key from one database to another Code Terminal window ``` redis-cli SELECT 0127.0.0.1:6379[0]> SET migration-key "data"127.0.0.1:6379[0]> MOVE migration-key 1127.0.0.1:6379[0]> SELECT 1127.0.0.1:6379[1]> GET migration-key ``` Execution ``` 1OK2(integer) 13"data" ``` - Returns 1 on success, 0 if key doesn't exist or destination exists - Useful for segregating data by type ## String Operations ### String Get and Set Operations Store and retrieve string values with various options #### Accessibility Beginner #### Best Practices - Use EX/PX directly in SET instead of separate EXPIRE command - Use MSET/MGET for multiple keys to reduce round trips - Use NX for locks and single-execution patterns - Validate JSON content before storing as strings #### Common Errors - **Value too large: 512MB is max, compress if needed:** - **SET with NX returns nil:** Key already exists, use DEL first if needed #### Keywords SETGETGETSETMGETMSET [Learn more](https://redis.io/commands/set/) #### Set and Get Simple String Basic string storage and retrieval Code Terminal window ``` redis-cli SET user:1:name "Alice"redis-cli GET user:1:name ``` Execution ``` 1OK2"Alice" ``` - Strings can be up to 512MB - GET returns nil if key doesn't exist #### Get Multiple Keys At Once Set multiple key-value pairs and retrieve them together Code Terminal window ``` redis-cli MSET user:1:name "Alice" user:2:name "Bob" user:3:name "Charlie"redis-cli MGET user:1:name user:2:name user:3:name ``` Execution ``` 1OK21) "Alice"32) "Bob"43) "Charlie" ``` - MGET is more efficient than multiple GET commands - Returns nil for non-existent keys in array #### Get and Set New Value Atomically Retrieve old value while setting new one in one operation Code Terminal window ``` redis-cli SET config:api-key "old-key-123"redis-cli GETSET config:api-key "new-key-456" ``` Execution ``` 1OK2"old-key-123" ``` - Returns BEFORE value, not after - Useful for rotating tokens or credentials #### Set with Expiration Options Set strings with automatic expiration in seconds (EX) or milliseconds (PX) Code Terminal window ``` redis-cli SET cache:homepage "..." EX 3600redis-cli SET cache:sidebar "{\"items\": [...]}" PX 5000 ``` Execution ``` 1OK2OK ``` - EX = expire in seconds, PX = expire in milliseconds - Common pattern for cache data #### Set Only If Key Doesn't Exist Use NX to set only if key doesn't exist Code Terminal window ``` redis-cli SET user:registration:lock "processing" NXredis-cli SET user:registration:lock "done" NX ``` Execution ``` 1OK2(nil) ``` - Returns OK on success, nil if key already exists - Useful for distributed locks and single-execution patterns #### Set Only If Key Already Exists Use XX to set only if key already exists Code Terminal window ``` redis-cli SET counter "0"redis-cli SET counter "1" XXredis-cli SET nonexistent "value" XX ``` Execution ``` 1OK2OK3(nil) ``` - XX = only update existing keys - Prevents creating new keys accidentally ### String Manipulation Commands Modify and manipulate string values #### Accessibility Intermediate #### Best Practices - Use APPEND for building logs or messages incrementally - Validate string length before SETRANGE to avoid unexpected results - Use GETRANGE for extracting parts (email domain, etc.) - Consider JSON if frequent string manipulation is needed #### Common Errors - **String not mutable like in programming languages:** Must use APPEND/SETRANGE - **Offset exceeds string length:** SETRANGE will extend with nulls #### Keywords APPENDSTRLENGETRANGESETRANGESUBSTR [Learn more](https://redis.io/commands/append/) #### Append to String Add text to end of existing string, returns new length Code Terminal window ``` redis-cli SET message "Hello"redis-cli APPEND message " World"redis-cli GET message ``` Execution ``` 1OK2(integer) 113"Hello World" ``` - If key doesn't exist, APPEND creates it - Returns the length of string after appending #### Get String Length Get length of string value in characters Code Terminal window ``` redis-cli SET filename "document.pdf"redis-cli STRLEN filename ``` Execution ``` 1OK2(integer) 12 ``` - Returns 0 for non-existent keys - O(1) operation #### Get Substring from String Extract substring using start and end positions Code Terminal window ``` redis-cli SET email "user@example.com"redis-cli GETRANGE email 0 3redis-cli GETRANGE email 5 -1 ``` Execution ``` 1OK2"user"3"example.com" ``` - Supports negative indices from end of string - \-1 means last character #### Set Substring in String Replace portion of string starting at offset Code Terminal window ``` redis-cli SET data "Hello World"redis-cli SETRANGE data 6 "Redis"redis-cli GET data ``` Execution ``` 1OK2(integer) 113"Hello Redis" ``` - Extends with null bytes if necessary - Returns length of resulting string ### String Numeric Operations Increment, decrement, and perform math on numeric strings #### Accessibility Intermediate #### Best Practices - Use INCR for atomic counters without race conditions - Use INCRBY for batch increments (multiple page views) - INCRBYFLOAT for metrics like temperature, prices - Always verify numeric format before INCR/DECR #### Common Errors - **ERR value is not an integer or out of range:** String is not numeric - **Negative numbers with INCR:** Results in negative counter, validate in code #### Keywords INCRDECRINCRBYDECRBYINCRBYFLOATGETEX [Learn more](https://redis.io/commands/incr/) #### Increment Integer Value Increment numeric string by 1, returns new value Code Terminal window ``` redis-cli SET counter "10"redis-cli INCR counterredis-cli GET counter ``` Execution ``` 1OK2(integer) 113"11" ``` - String must be valid integer format - Returns error if not numeric - Atomic operation, safe for concurrent access #### Increment by Specific Amount Add specific value to numeric string Code Terminal window ``` redis-cli SET page-views:today "1000"redis-cli INCRBY page-views:today 50 ``` Execution ``` 1OK2(integer) 1050 ``` - Works with negative values for subtraction - Useful for counters and metrics #### Decrement Value Decrement value by 1 or specific amount Code Terminal window ``` redis-cli SET inventory:item-5 "100"redis-cli DECR inventory:item-5redis-cli DECRBY inventory:item-5 10 ``` Execution ``` 1OK2(integer) 993(integer) 89 ``` - Useful for stock management - DECRBY with negative number acts as increment #### Increment Float Value Add decimal increment to numeric string Code Terminal window ``` redis-cli SET temperature "20.5"redis-cli INCRBYFLOAT temperature 0.3redis-cli GET temperature ``` Execution ``` 1OK2"20.8"3"20.8" ``` - Accuracy of 17 digits - Returns new value as string #### Get and Update Expiration Get value and update its expiration in one command Code Terminal window ``` redis-cli SET rate-limit:ip "5" EX 60redis-cli GETEX rate-limit:ip EX 120 ``` Execution ``` 1OK2"5" ``` - More efficient than GET + EXPIRE - Can also use EXAT, PERSIST options ### String Bit Operations Bitwise operations on string values #### Accessibility Advanced #### Best Practices - Use bit operations for compact flag/status storage - Combine with BITCOUNT to count set flags without reading them - Use BITOP for set operations on binary data - Document bit positions in comments for clarity #### Common Errors - **BITOP result needs storage:** Must specify dest key in BITOP - **Confusing byte vs bit positions:** BITCOUNT uses bytes, bit operations use bits #### Keywords SETBITGETBITBITCOUNTBITOPBITPOS [Learn more](https://redis.io/commands/setbit/) #### Set Individual Bit Set specific bit position and retrieve its value Code Terminal window ``` redis-cli SETBIT flags 7 1redis-cli GETBIT flags 7redis-cli GET flags ``` Execution ``` 1(integer) 02(integer) 13"\x01" ``` - Bit position is 0-indexed - Returns previous bit value - Useful for compact flag storage #### Count Set Bits Count number of 1 bits in string Code Terminal window ``` redis-cli SET bitmap "foobar"redis-cli BITCOUNT bitmap ``` Execution ``` 1OK2(integer) 26 ``` - Can specify byte range to count - Useful for HyperLogLog-like operations #### Bitwise Operations Between Values Perform AND operation between two string values Code Terminal window ``` redis-cli SET key1 "foobar"redis-cli SET key2 "abcdef"redis-cli BITOP AND dest key1 key2redis-cli GET dest ``` Execution ``` 1OK2OK3(integer) 64"`bc`ab" ``` - Supports AND, OR, XOR, NOT operations - Returns length of result #### Find First Set Bit Find position of first bit set to 1 Code Terminal window ``` redis-cli SETBIT bits 10 1redis-cli BITPOS bits 1 ``` Execution ``` 1(integer) 02(integer) 10 ``` - Can search for 0 bits as well - Returns -1 if no such bit exists ## List Operations ### List Push and Pop Operations Add and remove elements from list begins and ends #### Accessibility Beginner #### Best Practices - Use lists for queues and stacks (FIFO/LIFO patterns) - Batch pop operations to reduce network round trips - Avoid accessing middle elements frequently (use sets instead) - Monitor list length to detect unexpectedly large lists #### Common Errors - **Using LINDEX on large lists:** O(n) operation, slow for millions - **Empty list operations:** LPOP on empty list returns nil, not error #### Keywords LPUSHRPUSHLPOPRPOPLLENLINDEX [Learn more](https://redis.io/commands/lpush/) #### Push Elements to List Add elements to left (beginning) of list, returns list length Code Terminal window ``` redis-cli LPUSH notifications "message1"redis-cli LPUSH notifications "message2" "message3"redis-cli LLEN notifications ``` Execution ``` 1(integer) 12(integer) 33(integer) 3 ``` - LPUSH adds to beginning, RPUSH adds to end - Returns length after push operation - Can push multiple items at once #### Pop Elements from List Remove and return element from left or right side Code Terminal window ``` redis-cli LPOP notificationsredis-cli RPOP notificationsredis-cli LLEN notifications ``` Execution ``` 1"message3"2"message1"3(integer) 1 ``` - LPOP removes from beginning (newest first LIFO) - RPOP removes from end - Returns nil if list is empty #### Pop Multiple Elements Remove multiple elements from list in single command Code Terminal window ``` redis-cli RPUSH queue "task1" "task2" "task3" "task4"redis-cli LPOP queue 2 ``` Execution ``` 1(integer) 421) "task1"32) "task2" ``` - COUNT parameter specifies how many to pop - Reduces round trips for batch processing #### Get Element at Index Access element at specific position without removing it Code Terminal window ``` redis-cli LINDEX notifications 0redis-cli LINDEX notifications -1 ``` Execution ``` 1"message2"2"message1" ``` - 0 is first element, -1 is last element - Returns nil if index out of range - O(n) operation, slower for large lists #### Get List Length Return number of elements in list Code Terminal window ``` redis-cli LLEN notifications ``` Execution ``` 1(integer) 2 ``` - Returns 0 for empty or non-existent keys - O(1) operation ### List Range Operations Get, set, and trim ranges of list elements #### Accessibility Intermediate #### Best Practices - Use LRANGE with 0 -1 to get all elements (up to reasonable size) - LTRIM to keep only recent items (e.g., last 1000 messages) - Don't use LINSERT on large lists (O(n) operation) - Use LMOVE for atomic queue rotation #### Common Errors - **LSET on non-existent index:** Out of range error, size list first - **LINSERT with wrong pivot:** Returns -1, value not found in list #### Keywords LRANGELSETLTRIMLINSERTLMOVE [Learn more](https://redis.io/commands/lrange/) #### Get Range of Elements Get elements between start and end indices (inclusive) Code Terminal window ``` redis-cli RPUSH mylist "one" "two" "three" "four" "five"redis-cli LRANGE mylist 0 2redis-cli LRANGE mylist -2 -1 ``` Execution ``` 1(integer) 521) "one"32) "two"43) "three"51) "four"62) "five" ``` - Supports negative indices from end - 0 to -1 returns all elements - Returns empty array if range is invalid #### Trim List to Range Keep only elements in specified range, delete others Code Terminal window ``` redis-cli LTRIM mylist 0 2redis-cli LRANGE mylist 0 -1 ``` Execution ``` 1OK21) "one"32) "two"43) "three" ``` - Efficient way to limit list size - Commonly used to keep only recent items #### Set Element at Index Update element at specific position Code Terminal window ``` redis-cli LSET mylist 1 "TWO"redis-cli LINDEX mylist 1 ``` Execution ``` 1OK2"TWO" ``` - Returns error if index out of range - O(n) operation #### Insert Element Before or After Position Insert element before or after first occurrence of pivot value Code Terminal window ``` redis-cli LINSERT mylist BEFORE "TWO" "1.5"redis-cli LRANGE mylist 0 -1 ``` Execution ``` 1(integer) 421) "one"32) "1.5"43) "TWO"54) "three" ``` - Returns -1 if pivot not found - O(n) operation, slow for large lists #### Move Element Between Lists Atomically move element from source to destination list Code Terminal window ``` redis-cli RPUSH source "a" "b" "c"redis-cli LMOVE source dest LEFT RIGHTredis-cli LRANGE source 0 -1redis-cli LRANGE dest 0 -1 ``` Execution ``` 1(integer) 32"a"31) "b"42) "c"51) "a" ``` - LEFT=pop from left, RIGHT=pop from right - Destination receives from left or right - Useful for rotating between lists ### List Blocking Operations Block and wait for list operations with timeout #### Accessibility Advanced #### Best Practices - Use BLPOP for worker processes waiting on task queues - Set appropriate timeout (0 for infinite, or business timeout) - Use BRPOPLPUSH for task states (pending→processing→done) - Handle nil return when timeout occurs #### Common Errors - **Blocking forever:** Set reasonable timeout to prevent zombie connections - **Wrong order of arguments:** Timeout is last parameter #### Keywords BLPOPBRPOPBRPOPLPUSHBLMOVEtimeout [Learn more](https://redis.io/commands/blpop/) #### Blocking Pop Left Block until element available in list or timeout reached Code Terminal window ``` redis-cli BLPOP task-queue 0# On another client:# LPUSH task-queue "process-image.jpg" ``` Execution ``` 1# Waits until element available or timeout21) "task-queue"32) "process-image.jpg" ``` - Timeout 0 = wait forever - Returns \[key, value\] when element available - Multiple clients can block on same key #### Blocking Pop with Timeout Return nil if nothing available after 5 seconds Code Terminal window ``` redis-cli BLPOP empty-queue 5 ``` Execution ``` 1# Waits 5 seconds then returns nil2(nil) ``` - Timeout in seconds - Useful for poll-based checking #### Blocking Pop from Multiple Queues Wait for element from any of multiple lists Code Terminal window ``` redis-cli BLPOP queue1 queue2 queue3 0 ``` Execution ``` 11) "queue2"22) "item-from-queue2" ``` - Returns as soon as element available in any list - Last parameter is timeout - Useful for priority queue patterns #### Block and Move Between Lists Atomically pop from one list and push to another with blocking Code Terminal window ``` redis-cli BLMOVE source dest LEFT RIGHT 5 ``` Execution ``` 1"moved-element" ``` - Returns popped element or nil on timeout - Atomic operation, no race conditions #### Blocking Pop and Push Pattern Pop from pending, push to processing atomically Code Terminal window ``` redis-cli BRPOPLPUSH pending-tasks processing-tasks 10 ``` Execution ``` 1"task-123" ``` - Useful for task processing with automatic movement - Element stays in processing list until explicitly removed ## Set Operations ### Set Add and Remove Operations Manage set membership and size #### Accessibility Beginner #### Best Practices - Use sets for membership testing (fast O(1) lookups) - Use sets for unique collections (tags, followers, permissions) - Use SCAN for large sets instead of SMEMBERS - Batch SADD operations when possible #### Common Errors - **Using SMEMBERS on large set:** Returns all at once, may block server - **Expecting ordered results:** Sets have no order, use sorted sets if needed #### Keywords SADDSREMSCARDSMEMBERSSISMEMBER [Learn more](https://redis.io/commands/sadd/) #### Add Elements to Set Add members to set, duplicates are ignored Code Terminal window ``` redis-cli SADD tags "python" "redis" "database"redis-cli SADD tags "python"redis-cli SCARD tags ``` Execution ``` 1(integer) 32(integer) 03(integer) 3 ``` - Returns count of newly added members (not duplicates) - Second SADD returns 0 because "python" already exists #### Check Set Membership Check if element is member of set Code Terminal window ``` redis-cli SISMEMBER tags "python"redis-cli SISMEMBER tags "go" ``` Execution ``` 1(integer) 12(integer) 0 ``` - Returns 1 if member, 0 if not - O(1) operation #### Check Multiple Members Check membership of multiple elements in single command Code Terminal window ``` redis-cli SMISMEMBER tags "python" "redis" "go" ``` Execution ``` 11) (integer) 122) (integer) 133) (integer) 0 ``` - Returns array of 1/0 for each element #### Remove Elements from Set Remove members from set, returns count removed Code Terminal window ``` redis-cli SREM tags "database" "go"redis-cli SCARD tags ``` Execution ``` 1(integer) 12(integer) 2 ``` - Only "database" was removed (exists), "go" returned count 1 #### Get All Set Members Return all members of set (unordered) Code Terminal window ``` redis-cli SMEMBERS tags ``` Execution ``` 11) "python"22) "redis" ``` - Order is not guaranteed - Use SCAN for large sets to avoid blocking - Returns array of members ### Set Operations (Union, Intersection, Difference) Combine and compare sets #### Accessibility Intermediate #### Best Practices - Use SINTER for access control (user has all required permissions) - Use SUNION for OR logic (has role-A OR role-B) - Use SDIFF to find exclusive items (users who haven't redeemed) - Use \*STORE to cache results of expensive operations #### Common Errors - **Empty result from SINTER:** Check all sets contain expected members - **Wrong argument order for SDIFF:** First set minus others, not symmetric #### Keywords SINTERSUNIONSDIFFSINTERSTORESUNIONSTORESDIFFSTORE [Learn more](https://redis.io/commands/sinter/) #### Find Common Elements (Intersection) Find elements common to both sets Code Terminal window ``` redis-cli SADD users:online "alice" "bob" "charlie"redis-cli SADD users:premium "bob" "charlie" "dave"redis-cli SINTER users:online users:premium ``` Execution ``` 1(integer) 32(integer) 331) "bob"42) "charlie" ``` - Returns only members in ALL specified sets - Useful for finding users with multiple properties #### Combine All Elements (Union) Get all unique members from both sets Code Terminal window ``` redis-cli SUNION users:online users:premium ``` Execution ``` 11) "alice"22) "bob"33) "charlie"44) "dave" ``` - Combines all elements, removes duplicates - Useful for permissions (any admin OR any moderator) #### Find Unique Elements (Difference) Find elements in first set but not in others Code Terminal window ``` redis-cli SDIFF users:online users:premium ``` Execution ``` 11) "alice" ``` - Order of sets matter (first set minus others) - Useful for finding exclusive members #### Store Operation Result Perform operation and store result in new set Code Terminal window ``` redis-cli SINTERSTORE premium-online users:online users:premiumredis-cli SMEMBERS premium-online ``` Execution ``` 1(integer) 221) "bob"32) "charlie" ``` - \*STORE variants return count of result elements - Useful for caching computed results #### Find Multi-Set Intersection Find members in all three sets Code Terminal window ``` redis-cli SADD readers "alice" "bob" "charlie" "dave"redis-cli SADD writers "bob" "charlie" "eve"redis-cli SADD editors "charlie" "frank"redis-cli SINTER readers writers editors ``` Execution ``` 11) "charlie" ``` - Only "charlie" is in readers AND writers AND editors ### Set Advanced Operations Advanced set operations and management #### Accessibility Intermediate #### Best Practices - Use SPOP for removing random samples - Use SRANDMEMBER for sampling without removal - Use SMOVE for state transitions between sets - Use SSCAN for large sets instead of SMEMBERS #### Common Errors - **SPOP on empty set:** Returns nil without error - **SMOVE with non-existent member:** Returns 0, not error #### Keywords SPOPSRANDMEMBERSMOVESSCAN [Learn more](https://redis.io/commands/spop/) #### Remove and Return Random Member Remove and return random element(s) from set Code Terminal window ``` redis-cli SADD lottery-pool "ticket-1" "ticket-2" "ticket-3" "ticket-4" "ticket-5"redis-cli SPOP lottery-poolredis-cli SPOP lottery-pool 2 ``` Execution ``` 1(integer) 52"ticket-3"31) "ticket-1"42) "ticket-5" ``` - Single member removes one, with count removes multiple - Useful for random selection and removal (lottery, queue) #### Get Random Members Without Removal Return random members without removing them Code Terminal window ``` redis-cli SRANDMEMBER users:activeredis-cli SRANDMEMBER users:active 3 ``` Execution ``` 1"bob"21) "alice"32) "charlie"43) "bob" ``` - Count can exceed set size (with repetition) - Negative count allows duplicates #### Move Member Between Sets Move member from source set to destination set Code Terminal window ``` redis-cli SADD users:online "alice"redis-cli SMOVE users:online users:offline "alice"redis-cli SISMEMBER users:online "alice"redis-cli SISMEMBER users:offline "alice" ``` Execution ``` 1(integer) 12(integer) 13(integer) 04(integer) 1 ``` - Returns 1 if moved, 0 if not found in source - Atomic operation #### Scan Large Set Iterate through set using cursor without blocking Code Terminal window ``` redis-cli SSCAN users:active 0 COUNT 50 ``` Execution ``` 11) "2048"22) 1) "user:1"3 2) "user:2"4 3) "user:3" ``` - Returns \[cursor, \[members\]\] - Use cursor 0 to start, continue until 0 returned ## Hash Operations ### Hash Get and Set Operations Store and retrieve hash field-value pairs #### Accessibility Beginner #### Best Practices - Use hashes for multi-field objects (user profiles, configs) - Set multiple fields at once to reduce network calls - Use HSCAN for large hashes instead of HGETALL - Structure as hash instead of multiple strings for related data #### Common Errors - **Using HGETALL on large hash:** May block server, use HSCAN instead - **Field not found:** HGET returns nil, not an error #### Keywords HSETHGETHMSETHMGETHGETALLHDEL [Learn more](https://redis.io/commands/hset/) #### Set and Get Hash Fields Set multiple hash fields and retrieve individual ones Code Terminal window ``` redis-cli HSET user:1 name "Alice" email "alice@example.com" age "30"redis-cli HGET user:1 nameredis-cli HGET user:1 email ``` Execution ``` 1(integer) 32"Alice"3"alice@example.com" ``` - HSET can set multiple field-value pairs at once - Returns count of new fields added - HGET returns nil if field doesn't exist #### Get Multiple Hash Fields Retrieve multiple fields in single command Code Terminal window ``` redis-cli HMGET user:1 name age country ``` Execution ``` 11) "Alice"22) "30"33) (nil) ``` - Returns array with nil for non-existent fields - More efficient than multiple HGET calls #### Get All Hash Fields and Values Retrieve all field-value pairs from hash Code Terminal window ``` redis-cli HGETALL user:1 ``` Execution ``` 11) "name"22) "Alice"33) "email"44) "alice@example.com"55) "age"66) "30" ``` - Returns flattened array \[field1, value1, field2, value2, ...\] - For large hashes, use HSCAN to avoid blocking #### Delete Hash Fields Remove fields from hash, returns count deleted Code Terminal window ``` redis-cli HDEL user:1 age countryredis-cli HLEN user:1 ``` Execution ``` 1(integer) 12(integer) 2 ``` - "age" was deleted (1), "country" didn't exist (not counted) - HLEN shows remaining fields #### Check Field Existence Check if specific field exists in hash Code Terminal window ``` redis-cli HEXISTS user:1 nameredis-cli HEXISTS user:1 age ``` Execution ``` 1(integer) 12(integer) 0 ``` - Returns 1 if exists, 0 if not - O(1) operation ### Hash Numeric Operations Increment and perform math on hash fields #### Accessibility Intermediate #### Best Practices - Use HINCRBY for counters in hash fields - Use HINCRBYFLOAT for averaged metrics - Use HSETNX to prevent overwriting configured values - Validate numeric fields before incrementing #### Common Errors - **ERR hash value is not an integer:** Field contains non-numeric value - **HSETNX on existing field:** Returns 0, field not updated #### Keywords HINCRBYHINCRBYFLOATHSETNX [Learn more](https://redis.io/commands/hincrby/) #### Increment Integer Hash Field Decrement (negative increment) stock field in hash Code Terminal window ``` redis-cli HSET product:1 price 100 stock 50redis-cli HINCRBY product:1 stock -5redis-cli HGET product:1 stock ``` Execution ``` 1(integer) 22(integer) 453"45" ``` - Useful for inventory management - Returns new value after increment #### Increment Float Hash Field Add decimal value to hash field Code Terminal window ``` redis-cli HSET stats:page daily-avg 2.5redis-cli HINCRBYFLOAT stats:page daily-avg 0.3redis-cli HGET stats:page daily-avg ``` Execution ``` 1(integer) 12"2.8"3"2.8" ``` - Useful for floating point metrics - Returns new value as string #### Set Field Only If Doesn't Exist Set field only if it doesn't already have a value Code Terminal window ``` redis-cli HSETNX user:profile avatar "default.jpg"redis-cli HSETNX user:profile avatar "custom.jpg" ``` Execution ``` 1(integer) 12(integer) 0 ``` - Returns 1 if field set, 0 if already existed - Useful for defaults and initialization ### Hash Scanning and Enumeration Iterate through hash fields without blocking #### Accessibility Intermediate #### Best Practices - Use HKEYS/HVALS when you know hash is small - Use HSCAN for large hashes with millions of fields - Monitor HLEN to detect abnormal growth - Use field names with consistent prefixes for HSCAN patterns #### Common Errors - **HGETALL on large hash:** Can block server, use HSCAN instead - **MATCH in HSCAN without results:** Pattern might not match fields #### Keywords HSCANHKEYSHVALSHLENHSTRLEN [Learn more](https://redis.io/commands/hscan/) #### Get All Hash Field Names Return all field names from hash Code Terminal window ``` redis-cli HKEYS user:1 ``` Execution ``` 11) "name"22) "email"33) "phone" ``` - Order not guaranteed - Use HSCAN for large hashes instead #### Get All Hash Values Return all values without field names Code Terminal window ``` redis-cli HVALS user:1 ``` Execution ``` 11) "Alice"22) "alice@example.com"33) "555-1234" ``` - Returns array of values only #### Get Hash Field Count Count number of fields in hash Code Terminal window ``` redis-cli HLEN user:1 ``` Execution ``` 1(integer) 3 ``` - O(1) operation - Returns 0 for non-existent hash #### Scan Hash Fields with Pattern Scan hash fields matching pattern without blocking Code Terminal window ``` redis-cli HSCAN config:app 0 MATCH "*-timeout" COUNT 10 ``` Execution ``` 11) "2048"22) 1) "api-timeout"3 2) "30000"4 3) "db-timeout"5 4) "5000" ``` - Returns \[cursor, \[field1, value1, field2, value2, ...\]\] - Cursor-based iteration like SCAN #### Get String Length of Hash Field Value Return byte length of specific field's value Code Terminal window ``` redis-cli HSTRLEN user:1 email ``` Execution ``` 1(integer) 19 ``` - Useful for validation without retrieving value ## Sorted Sets Operations ### Sorted Set Add and Remove Operations Manage sorted set members with scores #### Accessibility Intermediate #### Best Practices - Use sorted sets for leaderboards, rankings, scored data - Use ZREVRANGE 0 n-1 for top-N queries - Batch ZADD operations to reduce round trips - Monitor ZCARD to detect unusual growth #### Common Errors - **Score is not a number:** Must be numeric or inf/-inf - **Confusing ZRANGE order: 0 is lowest score, not first added:** #### Keywords ZADDZREMZCARDZRANGEZREVRANGEZSCORE [Learn more](https://redis.io/commands/zadd/) #### Add Members with Scores Add members to sorted set with numeric scores Code Terminal window ``` redis-cli ZADD leaderboard 100 "player1" 150 "player2" 120 "player3"redis-cli ZCARD leaderboard ``` Execution ``` 1(integer) 32(integer) 3 ``` - Members sorted by score in ascending order - Duplicate members update score #### Get Range by Index Get members in score order, optionally with scores Code Terminal window ``` redis-cli ZRANGE leaderboard 0 -1redis-cli ZRANGE leaderboard 0 -1 WITHSCORES ``` Execution ``` 11) "player1"22) "player3"33) "player2"41) "player1"52) "100"63) "player3"74) "120"85) "player2"96) "150" ``` - 0 = lowest score, -1 = highest score - WITHSCORES returns interleaved scores #### Get Range in Reverse Order Get top scorers in descending order Code Terminal window ``` redis-cli ZREVRANGE leaderboard 0 2 WITHSCORES ``` Execution ``` 11) "player2"22) "150"33) "player3"44) "120"55) "player1"66) "100" ``` - ZREVRANGE returns highest scores first - Common pattern for leaderboards #### Get Member Rank Get position of member in sorted set Code Terminal window ``` redis-cli ZRANK leaderboard "player1"redis-cli ZREVRANK leaderboard "player1" ``` Execution ``` 1(integer) 02(integer) 2 ``` - ZRANK = position from low to high - ZREVRANK = position from high to low - 0-indexed #### Get Member Score Retrieve score of specific member Code Terminal window ``` redis-cli ZSCORE leaderboard "player2" ``` Execution ``` 1"150" ``` - Returns nil if member doesn't exist #### Remove Members Remove members from sorted set Code Terminal window ``` redis-cli ZREM leaderboard "player3" "nonexistent"redis-cli ZCARD leaderboard ``` Execution ``` 1(integer) 12(integer) 2 ``` - Returns count of actually removed members ### Sorted Set Range Queries Query sorted sets by score or lexicographical range #### Accessibility Intermediate #### Best Practices - Use ZRANGEBYSCORE for score-based filtering (ratings > 4.0) - Use ZCOUNT to quickly find count of items in range - Combine with LIMIT for pagination of large ranges - Use ZRANGEBYLEX for alphabetical listings #### Common Errors - **Wrong syntax for ranges:** Use (9 for exclusive, not <>9 - **ZRANGEBYLEX without equal scores:** Only works if all scores are equal #### Keywords ZRANGEBYSCOREZREVRANGEBYSCOREZRANGEBYLEXZCOUNTZLEXCOUNT [Learn more](https://redis.io/commands/zrangebyscore/) #### Get Members in Score Range Get all members with scores in range \[7, 9\] Code Terminal window ``` redis-cli ZADD product-scores 8.2 "item-1" 7.5 "item-2" 9.1 "item-3" 6.8 "item-4"redis-cli ZRANGEBYSCORE product-scores 7 9 WITHSCORES ``` Execution ``` 11) "item-2"22) "7.5"33) "item-1"44) "8.2"55) "item-3"66) "9.1" ``` - Inclusive range by default - Use (score for exclusive range #### Query with Score Limits Get range with exclusive upper bound and pagination Code Terminal window ``` redis-cli ZRANGEBYSCORE product-scores 7 (9 LIMIT 0 2 ``` Execution ``` 11) "item-2"22) "item-1" ``` - (9 means score < 9 (exclusive) - LIMIT offset count for pagination #### Get All Members with Minimum Score Use +inf for scores greater than value Code Terminal window ``` redis-cli ZRANGEBYSCORE product-scores 8 +inf ``` Execution ``` 11) "item-1"22) "item-3" ``` - \-inf for minimum scores - inf without + means non-existent #### Count Members in Score Range Count members without retrieving them Code Terminal window ``` redis-cli ZCOUNT product-scores 7 9 ``` Execution ``` 1(integer) 3 ``` - Returns count of members in range - O(log n) operation #### Lexicographical Range (Members with Equal Scores) Query members lexicographically when scores are equal Code Terminal window ``` redis-cli ZADD colors 0 "black" 0 "blue" 0 "green" 0 "red"redis-cli ZRANGEBYLEX colors "[b" "[g" ``` Execution ``` 11) "black"22) "blue"33) "green" ``` - All members must have same score - "\[" = inclusive, "(" = exclusive boundary ### Sorted Set Increment Operations Modify scores and manage sorted set members #### Accessibility Intermediate #### Best Practices - Use ZINCRBY to update scores atomically - Use ZPOPMIN for processing by priority - Use BZPOPMIN for worker processes - Validate score updates don't cause data anomalies #### Common Errors - **Score overflow:** Redis handles large numbers but plan for growth - **BZPOPMIN timing out:** Check if producer is adding items #### Keywords ZINCRBYZPOPMINZPOPMAXBZPOPMINBZPOPMAX [Learn more](https://redis.io/commands/zincrby/) #### Increment Member Score Increase score of member, returns new score Code Terminal window ``` redis-cli ZADD ratings user:1 4.5redis-cli ZINCRBY ratings 0.5 user:1redis-cli ZSCORE ratings user:1 ``` Execution ``` 1(integer) 12"5"3"5" ``` - Negative value decreases score - Creates member if doesn't exist #### Pop Lowest Scoring Member Remove and return lowest scoring members Code Terminal window ``` redis-cli ZPOPMIN priority-queue 2 ``` Execution ``` 11) "task-1"22) "1"33) "task-2"44) "2" ``` - Returns \[member1, score1, member2, score2, ...\] - Useful for processing queues by priority #### Pop Highest Scoring Member Remove and return highest scoring members Code Terminal window ``` redis-cli ZPOPMAX leaderboard 1 ``` Execution ``` 11) "player2"22) "150" ``` - Opposite of ZPOPMIN #### Blocking Pop Operations Block until lowest score member available Code Terminal window ``` redis-cli BZPOPMIN priority:queue 0 ``` Execution ``` 11) "priority:queue"22) "item-id"33) "1" ``` - Returns \[key, member, score\] on timeout nil - Useful for task processing ## Transactions & Scripting ### Transaction Basics Execute commands atomically with MULTI and EXEC #### Accessibility Intermediate #### Best Practices - Use transactions for related operations that must happen together - Keep transactions short to minimize lock contention - Use WATCH for optimistic locking on critical data - Handle nil return from EXEC (transaction aborted) #### Common Errors - **Can't nest MULTI:** Already in transaction raises error - **WATCH key changed:** EXEC returns nil, must retry logic #### Keywords MULTIEXECDISCARDWATCHatomic operations [Learn more](https://redis.io/commands/multi/) #### Simple Transaction Queue commands and execute atomically Code Terminal window ``` redis-cli127.0.0.1:6379> MULTI127.0.0.1:6379> SET key1 "value1"127.0.0.1:6379> SET key2 "value2"127.0.0.1:6379> GET key1127.0.0.1:6379> EXEC ``` Execution ``` 1OK2QUEUED3QUEUED4QUEUED51) OK62) OK73) "value1" ``` - Commands return QUEUED when in transaction - EXEC returns array of results - All commands execute or none if error #### Cancel Transaction Cancel transaction without executing queued commands Code Terminal window ``` redis-cli127.0.0.1:6379> MULTI127.0.0.1:6379> SET key1 "value"127.0.0.1:6379> DISCARD127.0.0.1:6379> GET key1 ``` Execution ``` 1OK2QUEUED3OK4(nil) ``` - DISCARD returns OK - All queued commands are discarded #### Monitor Key and Abort on Change Monitor key and only execute if unchanged Code Terminal window ``` redis-cli127.0.0.1:6379> SET account:1:balance "1000"127.0.0.1:6379> WATCH account:1:balance127.0.0.1:6379> MULTI127.0.0.1:6379> DECRBY account:1:balance 100127.0.0.1:6379> EXEC ``` Execution ``` 1OK2OK3OK4QUEUED51) (integer) 900 ``` - If key changed between WATCH and EXEC, transaction aborts - Returns nil if transaction aborted #### Optimistic Lock with WATCH Implement optimistic locking pattern Code Terminal window ``` redis-cli WATCH mykeyvalue=$(redis-cli GET mykey)# ... check value in application ...redis-cli MULTIredis-cli SET mykey "newvalue"# ... other commands ...redis-cli EXEC ``` Execution ``` 1OK2"oldvalue"3OK4QUEUED51) OK ``` - Application decides whether to commit - Useful for non-critical updates ### Lua Scripting Execute Lua scripts atomically on server #### Accessibility Advanced #### Best Practices - Use Lua for atomic operations combining multiple commands - Preload scripts with SCRIPT LOAD for frequent use - Keep scripts focused and simple for maintainability - Use EVALSHA after preloading to reduce network traffic #### Common Errors - **Script not found:** EVALSHA returns error if script not loaded - **KEYS vs ARGV indexing:** KEYS/ARGV are 1-indexed in Lua #### Keywords EVALEVALSHASCRIPT LOADSCRIPT FLUSHatomic Lua execution [Learn more](https://redis.io/commands/eval/) #### Execute Simple Lua Script Execute inline Lua script with zero keys Code Terminal window ``` redis-cli EVAL "return 'Hello from Lua'" 0 ``` Execution ``` 1"Hello from Lua" ``` - "0" = number of key arguments following - Script returns result to client #### Lua Script with Key and Argument Access Redis keys from Lua script Code Terminal window ``` redis-cli EVAL "return redis.call('GET', KEYS[1])" 1 mykey ``` Execution ``` 1"value" ``` - KEYS\[1\] = first key argument - ARGV indexing starts at 1 (not 0) #### Increment with Constraint Conditional increment only if under limit Code Terminal window ``` redis-cli EVAL "local current = redis.call('GET', KEYS[1])if tonumber(current) < tonumber(ARGV[1]) then redis.call('INCR', KEYS[1]) return 1endreturn 0" 1 counter 100 ``` Execution ``` 1(integer) 1 ``` - Atomic constraint check and update - Returns 1 if incremented, 0 if limit reached #### Preload Script with SHA Load script once, execute many times by SHA Code Terminal window ``` redis-cli SCRIPT LOAD "return 'cached script'"# Save SHA returned: abc123...redis-cli EVALSHA abc123... 0 ``` Execution ``` 1"abc123def456..."2"cached script" ``` - Reduces bandwidth for frequently used scripts - More efficient than EVAL for repeated calls #### Script Management Check script existence, clear cache, terminate running Code Terminal window ``` redis-cli SCRIPT EXISTS sha1 sha2 sha3redis-cli SCRIPT FLUSHredis-cli SCRIPT KILL ``` Execution ``` 11) (integer) 122) (integer) 03(integer) 34OK ``` - SCRIPT EXISTS returns array of 1/0 for each SHA - SCRIPT FLUSH clears script cache (careful in production!) ## Pub/Sub & Streams ### Pub/Sub Basics Publish and subscribe to message channels #### Accessibility Intermediate #### Best Practices - Use pub/sub for real-time notifications, not persistent queues - Publish count indicates delivery, but no guarantee of processing - Combine with persistence (streams) for critical messages - Use pattern subscriptions for dynamic channel names #### Common Errors - **Message loss if no subscribers:** Pub/sub doesn't queue messages - **Client stalled in subscribe mode:** Can't run other commands #### Keywords PUBLISHSUBSCRIBEUNSUBSCRIBEmessage broadcastchannels [Learn more](https://redis.io/commands/publish/) #### Subscribe to Channel Subscribe to "news" channel and wait for messages Code Terminal window ``` # Terminal 1redis-cli127.0.0.1:6379> SUBSCRIBE news ``` Execution ``` 1Reading messages... (press Ctrl-C to quit)21) "subscribe"32) "news"43) (integer) 1 ``` - Client blocks in subscribe mode - Receives confirmation message with subscription count #### Publish Message Publish message to channel Code Terminal window ``` # Terminal 2redis-cli PUBLISH news "Breaking news!" ``` Execution ``` 1(integer) 1 ``` - Returns number of subscribers that received message - Message sent immediately to all subscribers #### Receive Published Message Subscriber receives published message Code Terminal window ``` # Terminal 1 receiving ``` Execution ``` 11) "message"22) "news"33) "Breaking news!" ``` - Array format \[type, channel, message\] - Continues waiting for more messages #### Subscribe to Multiple Channels Subscribe to multiple channels at once Code Terminal window ``` redis-cli127.0.0.1:6379> SUBSCRIBE sports weather cryptocurrency ``` Execution ``` 1Reading messages...21) "subscribe"32) "sports"43) (integer) 151) "subscribe"62) "weather"73) (integer) 281) "subscribe"92) "cryptocurrency"103) (integer) 3 ``` - Subscription count increases per channel - Client receives messages from any subscribed channel #### Pattern Subscription Subscribe to channels matching pattern Code Terminal window ``` redis-cli PSUBSCRIBE "user:*:notification" ``` Execution ``` 11) "psubscribe"22) "user:*:notification"33) (integer) 1 ``` - Receives messages from matching dynamic channels - Pattern matching on server side ### Redis Streams Persistent, ordered message queues #### Accessibility Advanced #### Best Practices - Use streams for persistent, ordered message queues - Use consumer groups for distributed message processing - Acknowledge messages after processing to track progress - Monitor pending messages to detect stuck consumers #### Common Errors - **Group already exists:** XGROUP CREATE returns error if exists - **Format error in ID:** Must use milliseconds-sequence format #### Keywords XADDXREADXRANGEXGROUPstream consumer groups [Learn more](https://redis.io/commands/xadd/) #### Add Message to Stream Add messages to stream with auto-generated timestamp ID Code Terminal window ``` redis-cli XADD events "*" type "user_login" user "alice" ip "192.168.1.1"redis-cli XADD events "*" type "user_logout" user "bob" ``` Execution ``` 1"1704067200000-0"2"1704067201000-0" ``` - "\*" = auto-generate ID from milliseconds - ID format = timestamp-sequence #### Read Stream Range Read all messages in stream (oldest to newest) Code Terminal window ``` redis-cli XRANGE events - + ``` Execution ``` 11) 1) "1704067200000-0"2 2) 1) "type"3 2) "user_login"4 3) "user"5 4) "alice"6 5) "ip"7 6) "192.168.1.1"82) 1) "1704067201000-0"9 2) 1) "type"10 2) "user_logout"11 3) "user"12 4) "bob" ``` - "-" = minimum ID, "+" = maximum ID - Returns all messages with data #### Read New Messages from Position Read new messages after specific position Code Terminal window ``` redis-cli XREAD COUNT 2 STREAMS events "1704067200000-0" ``` Execution ``` 11) 1) "events"2 2) 1) 1) "1704067201000-0"3 2) 1) "type"4 2) "user_logout" ``` - Returns messages after provided ID - COUNT limits returned messages #### Create Consumer Group Create processor group and read undelivered messages Code Terminal window ``` redis-cli XGROUP CREATE events mygroup 0redis-cli XREADGROUP GROUP mygroup consumer1 STREAMS events ">" ``` Execution ``` 1OK21) 1) "events"3 2) 1) 1) "1704067200000-0"4 2) 1) "type"5 2) "user_login" ``` - "0" = start from beginning - ">" = new messages not yet delivered #### Acknowledge Message Processing Acknowledge processed message and check pending Code Terminal window ``` redis-cli XACK events mygroup "1704067200000-0"redis-cli XPENDING events mygroup ``` Execution ``` 1(integer) 121) (integer) 03 2) "1704067201000-0"4 3) "1704067201000-0"5 4) 1) 1) "consumer1"6 2) (integer) 1 ``` - XACK removes from pending list - XPENDING shows unacknowledged messages ## Advanced Features ### Persistence (RDB and AOF) Save and restore Redis data with RDB snapshots and AOF logs #### Accessibility Advanced #### Best Practices - Use AOF for critical data requiring durability - Use RDB for snapshots and faster recovery - Enable both for maximum protection - Monitor disk space used by persistence files #### Common Errors - **SAVE blocks server:** Use BGSAVE in production instead - **AOF file too large:** Schedule regular BGREWRITEAOF #### Keywords SAVEBGSAVEBGREWRITEAOFpersistence modesdata durability [Learn more](https://redis.io/commands/save/) #### Manual RDB Snapshot Create RDB snapshot synchronously (blocks server) Code Terminal window ``` redis-cli SAVE ``` Execution ``` 1OK ``` - Blocking operation, avoid in production - Saves to dump.rdb file #### Background RDB Snapshot Trigger RDB snapshot in background thread Code Terminal window ``` redis-cli BGSAVE ``` Execution ``` 1Background saving started ``` - Non-blocking, server continues operations - Check LASTSAVE for completion #### Check Last Save Time Get Unix timestamp of last successful RDB save Code Terminal window ``` redis-cli LASTSAVE ``` Execution ``` 1(integer) 1704067890 ``` - Returns seconds since epoch - Useful for monitoring backup freshness #### Rewrite AOF Log Trigger AOF log compaction in background Code Terminal window ``` redis-cli BGREWRITEAOF ``` Execution ``` 1Background append only file rewriting started ``` - Reduces AOF file size by removing redundant commands - Non-blocking operation ### Replication and Clustering Set up master-replica replication and Redis Cluster #### Accessibility Advanced #### Best Practices - Use replication for high availability - Monitor replication lag to detect issues - Test failover procedures regularly - Use cluster for automatic sharding at scale #### Common Errors - **Replication lag too high:** Network issues or slow replica disk - **Cluster slots unbalanced:** Rebalance using redis-cli --cluster #### Keywords REPLICAOFreplicationmaster-replicacluster nodesfailover [Learn more](https://redis.io/commands/replicaof/) #### Configure Replica Configure server as replica of master Code Terminal window ``` redis-cli REPLICAOF master-host 6379redis-cli INFO replication ``` Execution ``` 1OK2# Replication3role:slave4master_host:master-host5master_port:63796master_link_status:up7master_repl_offset:1234567 ``` - Starts syncing from master - Receives all write commands from master #### Stop Replication Stop replication and become standalone master Code Terminal window ``` redis-cli REPLICAOF NO ONE ``` Execution ``` 1OK ``` - Keeps data already synced - Stops receiving updates from old master #### Check Replica Lag Monitor master replication offset Code Terminal window ``` redis-cli INFO replication | grep master_repl_offset ``` Execution ``` 1master_repl_offset:9876543 ``` - Indicates how much data replica has from master #### Cluster Info Check Redis Cluster status Code Terminal window ``` redis-cli CLUSTER INFO ``` Execution ``` 1cluster_state:ok2cluster_slots_assigned:163843cluster_slots_ok:163844cluster_slots_pfail:05cluster_slots_fail:0 ``` - Shows slot distribution and health ### Memory Optimization Monitor and optimize Redis memory usage #### Accessibility Advanced #### Best Practices - Monitor used\_memory/used\_memory\_rss ratio for fragmentation - Set maxmemory-policy based on use case - Use volatile-lru for cache-like data - Use noeviction for critical non-expiring data #### Common Errors - **Out of memory:** Set maxmemory or eviction policy - **Wrong eviction policy:** Choose based on data type and use #### Keywords memory managementeviction policiesmaxmemorykey expirationmemory stats [Learn more](https://redis.io/commands/info/) #### Check Memory Stats Get detailed memory usage breakdown Code Terminal window ``` redis-cli INFO memory ``` Execution ``` 1# Memory2used_memory:10485763used_memory_human:1.00M4used_memory_rss:20971525used_memory_rss_human:2.00M6allocator_active:15728647allocator_allocated:10485768used_memory_peak:11000009used_memory_peak_human:1.05M ``` - used\_memory = Redis internal memory - used\_memory\_rss = OS allocated memory (higher due to fragmentation) #### Set Memory Limit Set max memory to 2GB with LRU eviction policy Code Terminal window ``` redis-cli CONFIG SET maxmemory 2147483648redis-cli CONFIG SET maxmemory-policy allkeys-lru ``` Execution ``` 1OK2OK ``` - Policies: noeviction, allkeys-lru, volatile-lru, allkeys-random, etc. - allkeys-lru = evict any key using LRU #### Eviction Policy Behavior How volatile-lru eviction picks keys Code Terminal window ``` # When maxmemory reached with volatile-lru:# Evicts keys with expiration, using LRU algorithm ``` Execution ``` 1# Only keys with TTL are eligible2# LRU tracks least recently used ``` - Applies only to keys with EXPIRE set - Safer than allkeys as it preserves important data #### Analyze Key Memory Usage Get Redis memory analysis and recommendations Code Terminal window ``` redis-cli --ldb# Alternative: MEMORY DOCTOR commandredis-cli MEMORY DOCTOR ``` Execution ``` 1Sam, I'm sorry. I don't see much to worry about...2# or detailed advice about memory issues ``` - Provides optimization suggestions - Shows potential memory leaks Was this useful? ## Share [Facebook](https://facebook.com/sharer/sharer.php?u=https%3A%2F%2Fmkabumattar.com%2Fcheatsheets%2Fredis "Share on Facebook")[Twitter](https://twitter.com/intent/tweet/?text=Redis&url=https%3A%2F%2Fmkabumattar.com%2Fcheatsheets%2Fredis "Share on Twitter")[LinkedIn](https://www.linkedin.com/shareArticle?mini=true&url=https%3A%2F%2Fmkabumattar.com%2Fcheatsheets%2Fredis&title=Redis&summary=Redis%20reference%20guide%20covering%20commands%2C%20data%20types%2C%20keys%2C%20strings%2C%20lists%2C%20sets%2C%20hashes%2C%20sorted%20sets%2C%20transactions%2C%20pub%2Fsub%2C%20and%20caching%20strategies.&source=https://mkabumattar.com "Share on LinkedIn")[WhatsApp](https://wa.me/?text=Redis%20https%3A%2F%2Fmkabumattar.com%2Fcheatsheets%2Fredis "Share on WhatsApp")[Telegram](https://t.me/share/url?url=https%3A%2F%2Fmkabumattar.com%2Fcheatsheets%2Fredis&text=Redis "Share on Telegram")[Reddit](https://www.reddit.com/submit?url=https%3A%2F%2Fmkabumattar.com%2Fcheatsheets%2Fredis&title=Redis "Share on Reddit")[Hacker News](http://news.ycombinator.com/submitlink?u=https%3A%2F%2Fmkabumattar.com%2Fcheatsheets%2Fredis&t=Redis "Share on Hacker News")[Pinterest](https://pinterest.com/pin/create/button/?url=https%3A%2F%2Fmkabumattar.com%2Fcheatsheets%2Fredis&media=&description=Redis%20reference%20guide%20covering%20commands%2C%20data%20types%2C%20keys%2C%20strings%2C%20lists%2C%20sets%2C%20hashes%2C%20sorted%20sets%2C%20transactions%2C%20pub%2Fsub%2C%20and%20caching%20strategies. 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