What is the difference between in-memory caching of an application and external cache (Redis)?

In-memory application caching and external caching, such as Redis, have different use cases and features:

• In-memory application cache:

  • Fast access since data is stored in the process's RAM.
  • Limited by memory and the application's lifecycle (data is lost upon restart).
  • Suitable for local caching, such as frequently used computed values.
  • Not suitable for distributed systems, as the cache is not shared between instances.

• External cache (Redis):

  • A separate service accessible over the network.
  • Allows caching data across different applications and instances.
  • Supports various data structures and lifetime management mechanisms.
  • More resilient to application restarts, as data can be stored in Redis server memory.