Performance

Cache

A fast, temporary copy of data so you don't redo expensive work every time.

A cache stores the result of something slow — a database query, an API call, a computed page — so the next request can grab the ready-made answer instead of recomputing it. It's the notepad on your desk: instead of walking to the filing cabinet (the database) every time someone asks the same question, you jot the answer down and read it off. The hard part is invalidation: knowing when the cached copy is stale and must be thrown away, or users see old prices and wrong data. Only cache once you have a real slowness problem — caching too early adds bugs where a fresh, simple query would have been fine.