[mannyv]

If your database is slow because it's on spinning disks, then a cache will speed up access.

That's not a fundamental mistake, and there's very little you can do about that from an efficiency point of view.

It's easy to forget that there was a world without SSDs, high speed pipes, etc - but it actually did exist. And that wasn't so long ago either.

And of course sometimes putting data nearer to the user actually makes sense...like the Netflix movie boxes inside various POPs or CDNs. Bandwidth and latency are actual factors for many applications.

That said, most applications probably should investigate adding indexes to their databases (or noSQL databases) instead of adding a cache layer.