Five mistakes teams make with caching layers

The advice here is unglamorous, which is probably why it gets skipped. These are the ones we run into repeatedly when we audit caching layers.

The right architecture for a team of three is the wrong one for a team of thirty, and vice versa. Budget a little time for it every quarter and it never becomes a project of its own.

The mistakes we see most

• Treating it as a launch task rather than an ongoing one
• Assuming someone else already owns it
• Caching is easy until something has to be invalidated
• Cache close to where the cost is, not everywhere
• Never checking whether the fix actually worked

A stale cache with no expiry is a future incident. None of that requires a large budget, only a decision and someone to own it. The teams that stay on top of it are the ones who put it on a calendar rather than a wish list.

Making it stick

The short version

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

The point is not perfection, it is knowing which of these you have consciously chosen to skip.