Next time you need to take a look at PHP, those two problems can be solved by php-apcu for caching and proxysql running side-by-side with php-fpm on each server.
I see comments like this an it always confuses me. AFAIK pooling or proxying a DB is actually worse for concurrent performance, because as soon as you hit the connection limit threads start waiting. It almost always makes sense to increase your DB capacity, or move hot data to a cache.
With apcu you're going to pay the cost of serializing/deserializing the data.
If you dump your read heavy data into a PHP file on disk, that just has a return of your generated data, you can be benefit from having that bytecode compiled data stored in opcache for free (for the entire lifetime of the php-fpm service, or until you reach the maximum opcache allocateable memory).
I think that PHP gives you a few nice utilities to handle sharing, but they are problem specific. For example you might also spawn threads within a background PHP task, and there is shared memory functionality you can use in that case as well which is going to be faster than apcu or opcache.
