Puppet and/or Ansible. I want it to be as easy to build servers as possible so that when a machine does go down, I can bring up another with little effort. This is very important for machines which I maintain that mostly run unattended save for maintenance every 6 months. I don’t have to dig up documentation, go through configuration files that I’m unfamiliar with, etc.
I just run Puppet, and the machine is configured in a known good state.
When it comes to evaluating technology, especially databases, I think that Call Me Maybe (https://aphyr.com/tags/jepsen) is required reading. The author of that blog puts database systems through their paces and breaks them in all sorts of interesting ways to test how well they really perform.