Redis Cheat Sheet

Updated 2026-04-27

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Redis is an in-memory data structure store used as a database, cache, and message broker. Its key mental model is that every key maps to exactly one data type and commands are valid only for that type. Redis 8 (GA 2025) unified what was previously Redis Stack — adding JSON, Time Series, Bloom filters, probabilistic structures, and the new Vector Set type (beta) directly into Redis Open Source. Day-to-day success with Redis comes from choosing the right structure (e.g., sorted sets for leaderboards, streams for event logs, vector sets for semantic search) and using safe key iteration (SCAN) plus explicit expiry (EXPIRE). Treat Redis as a long-running server you secure (ACL/TLS) and observe (INFO, SLOWLOG) rather than "just a library."

What This Cheat Sheet Covers

This topic spans 16 focused tables and 270 indexed concepts, 92 flashcards. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Setup and IntrospectionTable 2: Keys, TTL, and IterationTable 3: Strings and CountersTable 4: HashesTable 5: Lists and Blocking QueuesTable 6: SetsTable 7: Sorted Sets (ZSET)Table 8: StreamsTable 9: Pub/Sub and NotificationsTable 10: Bitmaps, HyperLogLog, and GeoTable 11: JSON (Redis 8)Table 12: Time Series (Redis 8)Table 13: Probabilistic Structures (Redis 8)Table 14: Vector Sets (Redis 8 — Beta)Table 15: Atomicity and ProgrammabilityTable 16: Operations, Security, and Scaling

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Table 1: Setup and Introspection

The commands you reach for first — connecting with redis-cli, confirming the server is alive, and peering into how it is configured and what it is doing. INFO, CONFIG GET/SET, and CLIENT LIST are your everyday windows into a running instance, and most config keys here can be changed live without a restart.

Concept	Example	Description
redis-cli	`redis-cli -h 127.0.0.1 -p 6379`	Connects to a Redis server from the command line.
PING	`PING`	Health check — returns `PONG` if server is reachable.
AUTH	`AUTH default myPassword`	Authenticates the current connection (username optional for single-password setup).
SELECT	`SELECT 1`	Switches to a logical database (0–15 by default).
DBSIZE	`DBSIZE`	Returns number of keys in the currently selected database.
INFO	`INFO memory`	Returns server stats and state, optionally filtered by section.
CONFIG GET	`CONFIG GET maxmemory`	Reads effective runtime configuration values.
CONFIG SET	`CONFIG SET maxmemory 1073741824`	Changes supported runtime configuration without restart.
CLIENT LIST	`CLIENT LIST`	Lists connected clients and metadata for each connection.
HELLO	`HELLO 3`	Switches protocol mode and returns server/connection info (use `3` for RESP3).
FLUSHDB	`FLUSHDB ASYNC`	Deletes all keys in the current database asynchronously.
SWAPDB	`SWAPDB 0 1`	• Atomically swaps two logical databases • fast and safe in-place swap.
LASTSAVE	`LASTSAVE`	Returns UNIX timestamp of last successful RDB save.
Install Redis Open Source	`redis-server --version`	Installs Redis and verifies the server binary is available.
redis.conf	`maxmemory 1gb` `maxmemory-policy allkeys-lru`	Defines Redis runtime configuration settings.

Table 2: Keys, TTL, and Iteration

Everything that treats keys generically — regardless of which data type sits behind them. The two habits worth burning in here: always prefer SCAN over KEYS so you never block the server walking a large keyspace, and lean on the rich expiry family (EXPIRE, PEXPIRE, EXPIREAT, and their TTL readers) since automatic eviction is how Redis stays a cache and not a memory leak. The OBJECT subcommands let you peek at internal encodings and access patterns when you are tuning memory.

Command	Example	Description
SET	`SET k "v" EX 60 NX`	Sets a key value with optional expiry, and conditions (`NX`=only if absent, `XX`=only if present).

The rest of this section is part of the full cheat sheet

Table 3: Strings and Counters

The string is Redis's simplest and most versatile type — it holds raw bytes, text, or an integer, and that integer side is what powers atomic counters. Because INCR and friends are single-operation atomic, they are the canonical way to build page-view tallies, rate limiters, and stock counts without race conditions. The GETEX/GETDEL pair folds a read together with an expiry update or delete, handy for one-shot tokens.

Concept	Example	Description
Strings	`SET k "v"`	Basic value type storing bytes, text, or integers up to 512 MB.

The rest of this section is part of the full cheat sheet

Table 4: Hashes

When a key needs to hold several named fields — think a user object with name, age, and logins — a hash stores them all under one key and stays remarkably memory-efficient for small objects. You can read or write individual fields without fetching the whole structure, atomically bump numeric fields with HINCRBY, and iterate large hashes safely with HSCAN.

Concept	Example	Description
Hashes	`HSET user:1 name "Ada" age "37"`	• Stores field/value pairs under one key • memory-efficient for small objects.

The rest of this section is part of the full cheat sheet

Table 1: Setup and Introspection

Concept	Example	Description
redis-cli	`redis-cli -h 127.0.0.1 -p 6379`	Connects to a Redis server from the command line.
PING	`PING`	Health check — returns `PONG` if server is reachable.
AUTH	`AUTH default myPassword`	Authenticates the current connection (username optional for single-password setup).
SELECT	`SELECT 1`	Switches to a logical database (0–15 by default).
DBSIZE	`DBSIZE`	Returns number of keys in the currently selected database.
INFO	`INFO memory`	Returns server stats and state, optionally filtered by section.
CONFIG GET	`CONFIG GET maxmemory`	Reads effective runtime configuration values.
CONFIG SET	`CONFIG SET maxmemory 1073741824`	Changes supported runtime configuration without restart.
CLIENT LIST	`CLIENT LIST`	Lists connected clients and metadata for each connection.
HELLO	`HELLO 3`	Switches protocol mode and returns server/connection info (use `3` for RESP3).
FLUSHDB	`FLUSHDB ASYNC`	Deletes all keys in the current database asynchronously.
SWAPDB	`SWAPDB 0 1`	• Atomically swaps two logical databases • fast and safe in-place swap.
LASTSAVE	`LASTSAVE`	Returns UNIX timestamp of last successful RDB save.
Install Redis Open Source	`redis-server --version`	Installs Redis and verifies the server binary is available.
redis.conf	`maxmemory 1gb` `maxmemory-policy allkeys-lru`	Defines Redis runtime configuration settings.

Table 2: Keys, TTL, and Iteration

Command	Example	Description
SET	`SET k "v" EX 60 NX`	Sets a key value with optional expiry, and conditions (`NX`=only if absent, `XX`=only if present).

Table 3: Strings and Counters

Concept	Example	Description
Strings	`SET k "v"`	Basic value type storing bytes, text, or integers up to 512 MB.

Table 4: Hashes

Concept	Example	Description
Hashes	`HSET user:1 name "Ada" age "37"`	• Stores field/value pairs under one key • memory-efficient for small objects.