I like using postgres for everything, it lets me simplify infrastructure. But using it as a cache is a bit concerning in terms of reliability, in my opinion.
I have witnessed many incidents when DB was considerably degrading. However, thanks to the cache in redis/memcache, a large part of the requests could still be processed with minimal increase in latency. If I were serving cache from the same DB instance, I guess, it would cause cache degradation too when there are any problems with the DB.
I have witnessed many incidents when DB was considerably degrading. However, thanks to the cache in redis/memcache, a large part of the requests could still be processed with minimal increase in latency. If I were serving cache from the same DB instance, I guess, it would cause cache degradation too when there are any problems with the DB.