Redis is an in-memory data storage system that provides high-performance caching and data persistence capabilities. The duration for which Redis stores data depends on various factors and configuration settings.
Volatile Data: Redis allows you to set an expiration time Time To Live(TTL) for individual keys. Once the TTL expires, Redis automatically removes the key and associated data from memory. This feature is commonly used for caching purposes, where data is expected to be valid for a certain duration. Once the TTL is reached, Redis evicts the data from memory, and subsequent requests for that data will result in a cache miss.
Persistent Data: Redis also supports data persistence to disk, which allows you to store data beyond the lifespan set by TTL. There are two main persistence options in Redis:
Here's an example of configuring both RDB and AOF persistence in Redis (in the redis.conf file):
With proper configuration, Redis can store data for an extended period. However, it's important to note that Redis is primarily an in-memory database, and the amount of data you can store is limited by the available memory. If the dataset size exceeds the memory capacity, Redis may evict less frequently accessed or expired keys to make room for new data.
It's also worth mentioning that the persistence mechanisms (RDB and AOF) can introduce disk I/O overhead, potentially impacting the performance of Redis. Therefore, the duration for which Redis stores data is a trade-off between memory capacity, desired TTLs, and the need for persistence.