Redis is an in-memory data structure store. It excels at caching, session storage, rate limiting, pub/sub, and leaderboards. Key data structures: Strings (SET/GET with TTL), Hashes (HSET/HGETALL for objects), Lists (LPUSH/RPOP for queues), Sorted Sets (ZADD/ZRANGE for leaderboards), Streams (XADD/XREAD for event logs). All commands are atomic. Lua scripts run atomically. Redlock is the distributed mutual-exclusion algorithm across multiple Redis nodes.
Each stage in order — click any step to read what it does.
Redis data structures and their primary use cases.
The trade-offs worth knowing before you build this.
KEYS * scans all keys — O(N) and blocks the single-threaded Redis during scan. Use SCAN 0 MATCH pattern COUNT 100 with cursor iteration instead.
PUBLISH/SUBSCRIBE loses messages if no subscriber is connected. Use Streams (XADD/XREADGROUP) for durable, acknowledged, consumer-group-based messaging.
Cache keys without TTL grow forever until eviction policy kicks in. Set EX at write time. Monitor memory with INFO memory and keyspace.
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