Cache Warming

Caching works well when the data your users need is already close to the application.

The difficult moment is the first few minutes after a deploy, cache restart, large scale-out event, or bulk invalidation. The application is healthy, but the cache does not yet contain the data needed for normal traffic. Requests that usually return from memory now fall through to the database or another backing service.

That is the cold cache problem.

Cache warming reduces this risk by loading important data into the cache before the full production workload depends on it.

In this chapter, we will cover what cache warming means, why cold caches cause incidents, when cache warming is worth the extra work, the common warming strategies, how to choose what to warm, and the production practices that keep warming safe.