I want to host a Rails/Postgres app. Is Redis required to install?

Why doesn’t fly.io allow us to omit the use of Redis? It seems like Redis is required.

I’m thinking about keeping things simple and simply have Rails communicate directly with the PG server.

It is NOT required. Take a look at: Existing Rails Apps · Fly Docs

Specifically the line that looks like:

? Would you like to set up an Upstash Redis database now?

Feel free to answer no to that question. That being said, you will want to have a redis server if you do any of the following: (1) action cable, (2) caching, or (3) use sidekiq. If none of these apply to you, say no to redis.