Do you also offer some kind of abstraction libraries when e.g. working with DynamoDB on AWS and then switching to GCP? Or would I still have to prepare my code for that?
Things like Dynamo are AWS-specific, it is their way of locking you in. You could use MongoDB or Cassandra (which is right depends on what you use it for) that would work in any cloud provider. Moreover, for 90% of use cases the capabilities of good old PostgreSQL are more than sufficient, even if you store JSON in it and use it like a document DB.
Yes, for folks who do not know, you can use Scylla, a NoSQL database that has a DynamoDB-compatible API, to deploy to other clouds (GCP) or even on-premises. It's been running in production for some years now. Here's the blog when we announced it, and there's more to be found on ScyllaDB.com — just search for "Alternator."