Introduction

An in-memory data store, keeps data in RAM for super-fast read/write speeds.

• Data is key-value based.

• Single-threaded execution (hence atomicity by default)

  • No locking overhead
  • No context switching
  • No race conditions inside Redis

• Keep data in memory, but can also persist to disk (optional):

  • RDB (Snapshotting)
    • Saves periodically.
    • Faster startup
    • Some data loss possible
  • AOF (Append Only File)
    • Logs every write operation for durability.
    • Slower but safer

  // can be hybrid

• Supports advanced data structures (not just strings).

// Also support Bitmaps, HyperLogLogs, Streams, Geospatial indexes.

Used for:

• Caching:
  • Store database query results to reduce DB load.
• Session management:
  • Store user sessions in memory for fast access.
• Leaderboards / counters:
  • Use sorted sets to maintain rankings.
• Pub/Sub notifications:
  • Real-time chat, notifications, or events.
• Rate limiting:
  • Count requests per IP to prevent abuse.

Redis is NOT:

• ❌ Frontend tool
• ❌ Replacement for relational databases