A bit of a plug, but if you wish for something that has the Postgres reliability, the taste of nosql but with strong typing and a json output a la graphql, give a try to edge db:
I feel like this is close to what I'm looking for but not quite there in terms of minimal boilerplate backend. Basically what I want to do is write a GraphQL schema and have that be the ultimate source of truth. The schema then should generate the full DB (honestly I don't even care if it's SQL, NoSQL, etc. the idea is that part is abstracted away). Then the schema can generate fully typesafe queries for the front end and serverless functions, similar to what graphql codegen does. I'm almost there with Hasura, but Hasura still requires definition on the DB side and generates the GraphQL rather than the other way around.
I'm wondering how FaunaDB's GraphqL would suit you? It's basically: "drop in schema, get API". You can't do everything that you'll ever need yet but you can go quite far and the implementation of each query is efficient since every query is one query and thus one transaction, is backed by indexes that are automatically generated and finally we are quite suitable for GraphQL-like queries. (because those are a bit like tree-walking queries for which the 'Index-free Adjacency' concept in graph databases is very suitable and FaunaDB's References are quite similar. Although we're not a Graph database we don't have problems with huge graph-like joins because of that. besides that, the compatibility of our native FQL language made it ridiculously easy to generate an FQL query GraphQL queries)
If there is something missing in our GraphQL feature set, feedback is very welcome :).
https://edgedb.com
The team behind it is awesome (one is a python core dev), and it's a FOSS, but they have been using it internally for some time.