The real cost of ignoring caching layers

The advice here is unglamorous, which is probably why it gets skipped. Nobody bills you for neglecting caching layers. The cost shows up somewhere else.

Architecture is the set of decisions that are expensive to reverse, which is the only reason they deserve the name. Budget a little time for it every quarter and it never becomes a project of its own.

Where the cost lands

• Time spent on work that should not have been necessary
• Enquiries that quietly never arrive
• Caching is easy until something has to be invalidated
• Rework, once the problem is finally visible

Cache close to where the cost is, not everywhere. In practice this is a scheduling problem more than a technical one. If it only works because one person remembers to do something, it does not work yet.

What to do next

A stale cache with no expiry is a future incident. Where this goes wrong is almost never a lack of knowledge. If it only works because one person remembers to do something, it does not work yet.

In practice

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
• Caching is easy until something has to be invalidated — and you know whether that is true here
• There is a way to tell whether the last change to this helped

If any of that sounds like a description of your current setup, it is fixable.