A client we are doing some work for is using Cassandra as their database. They run 10s of millions transactions a day and need 100% uptime. Cassandra seem to out perform mysql on this specific uptime consisntacy 10-1. I have watched extensive videos on this and cant seem to agree that this makes sense for them. So for them we will have to use it. So trying to find if phalcon supports it, which you say it doesnt, and if not trying to find the best php library to use.
Some of the applications we develop for ourselves are running a few million transactions a day too. Based on the work we will do for the client we might switch over our databases too.