pgxmock VS FerretDB

It's not the right call IMO to skip mocking the database connection to achieve 100% test coverage. How your app will behave in failure scenarios that are impossible to imitate during integration tests is part of the software contract. If your choice is to panic, or return an error, document that by testing that behavior. If another dev, or future you inadvertently breaks the contract, the test suite will fail. That's what you want. For unit tests against your database you should be using either go-sqlmock if testing against database/sql or pgxmock if testing against pgx. That being said, the points raised elsewhere in this thread regarding unit tests potentially hiding edge cases in terms of how an actual database will interact with your application that are not reflective of your understanding when writing mocks are 100% valid. You should do both. Unit test your app and write integration tests as well. On my team, we run integration tests using docker-compose.

For postgres only but pgxmock is similarly excellent

if you have postgres, just use https://github.com/FerretDB/FerretDB

FerretDB is an open source document database that adds MongoDB compatibility to other database backends, such as Postgres and SQLite. By using FerretDB, developers can access familiar MongoDB features and tools using the same syntax and commands for many of their use cases.

There is FerretDB. But they are not fully compatible to Mongo yet.

https://www.ferretdb.io/

Feature parity progress with apps:

https://github.com/FerretDB/FerretDB/issues/5

I presume, that after there is feature parity, then someone could run some benchmarks.

Yep that's serious issue and it's similar to our case. Our main product can work just fine even without SSE 4.2 but MongoDB requires it and then indirectly leads to AVX1 support as we use MongoDB as storage. We did PoC with FerretDB last month and I think it may be good option for Gerylog: https://www.ferretdb.io

Shout out to FerretDB, which is an in progress open source re-implementation of MongoDB atop PostgreSQL.

https://github.com/FerretDB/FerretDB