Redis Explained


  • Redis (REmote DIctionary Service) - key-value db
  • In-memory database, backup to disk
  • Use as cache in the past
  • Like Memcached, but more features
  • Many architecture configurations supported
    • Single instance - Main db only
    • HA (High Availability) - Has replications to secondary db
    • Sentinel - Has Sentinel(s) to monitor main & secondaries
    • Cluster - Horizontal scaling, gossipping nodes
  • Many persistence models
    • No persistence
    • RDB (Redis Database) file - Save db as file snapshot, faster than AOF
    • AOF (Append Only File) - Log write operations to be replayed again, more durable that RDB
      • Flushes to disk with fsync when possible
    • RDB + AOF - More durable but slower
  • Forking - OS creates process copy, but shares memory with copy-on-write technique
    • Redis uses this technique to persist the data performantly.