Cache

Cache is a temporary copy of data — a page, an image, an API response — saved somewhere closer or cheaper to read, so the system doesn’t have to fetch or compute it again every time.

Browsers cache assets locally. Servers and CDNs cache popular files at the edge. Apps cache query results in memory (tools like Redis). Good caching improves speed and Core Web Vitals; bad caching serves stale prices or a broken page after a deploy. The craft is deciding what to cache, how long, and when to invalidate.

A real-life example of a cache

A busy café prep station keeps the most-ordered drinks half-ready. Regulars get served faster; the kitchen isn’t remaking every latte from zero. When the menu changes, they clear the prep — same idea as busting cache after a site update.

Anonymous product pages and static images are great cache candidates. Personal carts and live stock usually aren’t. For practical tips, see Scale Without Tears and What’s the Deal with CDNs?.