Redis is an in-memory data store used for caching, session management, real-time leaderboards, message queues, and pub/sub messaging. It stores data in memory for sub-millisecond reads and writes, making it the go-to choice for speed-critical operations.

How Redis Works

Redis is typically used alongside a primary database. PostgreSQL stores your data permanently; Redis caches frequently-accessed data in memory for instant retrieval. A database query taking 50ms becomes a Redis lookup taking 0.1ms.

Beyond caching, Redis supports data structures: sorted sets for leaderboards, streams for event logs, pub/sub for real-time messaging, and HyperLogLog for counting unique visitors. Redis Stack adds JSON, search, and graph capabilities.

Key Concepts

  • In-Memory Storage — All data lives in RAM — sub-millisecond latency for reads and writes
  • Data Structures — Strings, lists, sets, sorted sets, hashes, streams — not just key-value
  • TTL (Time-To-Live) — Automatically expire keys after a duration — perfect for caches and sessions
  • Pub/Sub — Publish messages to channels that multiple subscribers receive in real time

Learn Redis — Top Videos

Frequently Asked Questions

Do I need Redis?

If your app has slow database queries, needs session storage, real-time features, or rate limiting — yes. Redis solves these with minimal complexity.

What happens if Redis crashes?

Redis supports persistence (RDB snapshots, AOF logging) and replication. For caching, data loss is acceptable — the cache rebuilds from the primary database.

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