[driverdan]

TL;DR: Everything has its place, stop implying you should never use use something.

> Don't use MongoDB.

Don't use MongoDB for something that should be in a relational DB. Use it as the document DB it is. Use the right tool for the right job. Mongo and other document DBs have their place.

> Don't use high level ORMs. Stay (reasonably) close to SQL. And yes, it should be SQL. Almost certainly Postgres.

Hard disagree. I've used many of the ORMs in different popular frameworks. They work well, save time, and are especially good for simple queries. They have their place, just as SQL does.

> Especially don't use Mongoid.

Unfortunately it's the go-to Ruby library for mongo. This could be an argument for not using mongo with Ruby. It could be an argument for creating an alternative. But simply saying don't use it isn't practical for many people.