I'd pick PostgreSQL over CouchDB because it is so common, has great documentation, and many people say it is a great default choice. For quickly launching an A

I'd pick PostgreSQL over CouchDB because it is so common, has great documentation, and many people say it is a great default choice. For quickly launching an API enabled backend, maybe look at encore.dev? It's not one of your listed languages (it's go), but at least it looks somewhat like C. I recently had to launch an API for a hackathon, and this was as fast as Ruby on Rails for me. Comes out of the box with Postgres and PubSub (2 lines of code if you need it). Encore also does the infra provisioning and hosting for you (either your cloud, or for free at their cloud). Tip: add `sqlc` for the queries, it works well together with Encore. GraphQL/REST: it looks like your app will have a limited set of calls that are easy to predefine. In that case, REST wins hands down. IMO GraphQL really shines if you have (a) a data model with many relations, (b) possibly from different underlying systems/services, and/or (c) different people working on the front-end/consumption side vs the data exposure side. But that's beyond 'a simple app'. Other tip: if you're thinking of building an admin interface. Don't, just use something like Retool first while you're getting users.