Redis Explained

Source

• 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.