What is Cache?

What is Cache?

A cache keeps frequently used or expensive-to-produce data in a faster temporary layer. The goal is to avoid recalculating or refetching the same data from a database, remote API, or origin server on every request.

Caching can happen in the browser, on a CDN, inside application memory, in an external service such as Redis, or near the database query layer. Product category lists, non-price catalog data, static assets, and precomputed report summaries are common candidates.

How Is It Designed?

A cache key identifies what is being stored. TTL defines how long the value is considered valid. Invalidation defines how old data is removed when the source changes. Many caching problems come not from storing data, but from failing to clear or refresh it at the right time.

Poor cache design can show stale prices, outdated inventory, or even data belonging to another user. Personal data, permission-based content, and payment results need stricter handling than public static assets.

Redis is a common application-level cache. A CDN caches static files and selected HTTP responses at edge locations near users.