Database

I chose to go with Cockroach DB for the database layer. This is because it shares a lot of the same scaling principals as Elixir. It scales horizontally. A single node can not take down the whole cluster. It's simple to upgrade in a rolling release (very helpful for Fly.io). And lastly, it has a very useful web interface to help debug slow queries. I won't go into too much detail about the benefits, but know that there are quite a bit. On the Elixir side, we use the standard Postgrex module to connect and run mostly the standard setup. Once thing of note is that during tests, we use a unique sandbox module to work around nested transactions. See this ecto issue for more details.