Redis persistence ensures your data survives server restarts, crashes, or power failures. By default, Redis stores data in memory, so without persistence, all data would be lost if the server stops. Persistence mechanisms give you options to balance performance and durability based on your needs.

Redis uses two main persistence methods: RDB snapshots and AOF logging.

RDB snapshots create point-in-time copies of your dataset at specified intervals. When a snapshot is triggered, Redis saves the current state of your data to an .rdb file on disk. This method is efficient for backups and disaster recovery, but any changes made after the last snapshot and before a crash will be lost.

AOF logging (Append Only File) records every write operation received by the server. Redis appends each command to an .aof file, allowing you to reconstruct the dataset by replaying these commands. AOF provides greater durability than RDB because you can configure Redis to flush the log to disk every second, minimizing data loss. However, AOF files can grow large and may require more disk space and processing time during recovery.

Persistence matters when you need to protect against data loss. Imagine you are running an online shopping cart in Redis. If the server crashes and you have no persistence enabled, all active carts disappear, frustrating customers and impacting sales. By enabling RDB or AOF, you ensure shopping carts are recovered after a restart, keeping your users' data safe and your service reliable.

Understanding these mechanisms helps you choose the right balance between performance and durability for your Redis deployment.