I understand that this is a shameless plug but I've met teams where the first response to any performance problem is caching

If you're reading this and have performance issues look at caches as a last resort, first figure out why things are slow

I'm assuming a traditional stack here but use mysql jet profiler, or SQL equivalent first, then your languages profiler xhprof?

If your queries are slow or impossible make sure your tables are normalised and indexed, make sure opcache is on and xdebug off

Mysql out of the box is very conservative with its resources, the limits can often be raised and the web server can often be configured to be faster, make sure you're sending the correct http cache headers

There's so many things to consider with performance Please don't denormalise your data slap it in redis/ use varnish and call it a day

No cache is free, eventually you have to pay the pied piper when you do make sure you can afford to have never used the cache at all

Some of my hardest bugs have come from out of sync caches & trying to build performant data architecture around systems that had data stuffed into a redis black hole aged for years..