Signs it is time to revisit caching layers

The advice here is unglamorous, which is probably why it gets skipped. A few signals that caching layers is due some attention.

The right architecture for a team of three is the wrong one for a team of thirty, and vice versa. The failure mode is not doing it wrong, it is doing it once and assuming it stays done.

The signals

• Nobody can say when it was last reviewed
• The answer depends on who you ask
• Caching is easy until something has to be invalidated
• Cache close to where the cost is, not everywhere

The practical version

A stale cache with no expiry is a future incident. There is a version of this that is over-engineered, and it is worth avoiding. Budget a little time for it every quarter and it never becomes a project of its own.

How to tell if yours is fine

Most systems fail at the seams rather than inside any one component. Three things worth confirming about caching layers before you move on:

• Someone can say what the current setup is without going to look
• Cache close to where the cost is, not everywhere — and you know whether that is true here
• There is a way to tell whether the last change to this helped

Worth checking on your own setup before it becomes someone else's problem to fix.