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Caching

Different kind of caching exists:

  • in-memory caching
  • distributed caching
  • content caching
  • database caching

Distributed caching

A distributed cache is a cache shared by multiple app servers, typically maintained as an external service to the app servers that access it.

How can I make sure that the external service is (accessed) fast?

When cached data is distributed, the data:

  • Is coherent (consistent) across requests to multiple servers.
  • Survives server restarts and app deployments.
  • Doesn't use local memory.

.NET Core provides these implementations:

  • Distributed Redis cache
  • Distributed Memory Cache
  • Distributed SQL Server cache
  • Distributed NCache cache

Redis is an open source in-memory data store.
in-memory --> fast
can be persisted as well

The in-memory distributed cache isn't actually a distibuted cache but might be useful if only a single server is used. It allows to easily implement a true distributed cache later.

SQL Server cache allows complex queries since it is a relational DB.

Redis is generally recommended as a distributed cache solution

.NET 9 will introduce a new cache called HybridCache. This should replace in memory and distributed caches. It provides one interface to support both in memory and distributed caches. It is in memory by default, allows stampede protection and can be extended to be distributed by adding (i.e.registering) a distributed cache like Redis.