Apparently, they are using a 1:1 mapping between a collection and a table. Either by flattening the document or by using jsonb or equivalent. I'm not a big believer this is good for performance reasons, at least compared to a more normalized approach like the one we did for https://www.torodb.com But they may change it in the future --if they don't expose the SQL API to their internal representation.
I led a C# project where we could seamlessly switch back and forth between Mongo and SQL Server without changing the underlying LINQ expressions.
We sent the expressions to the Mongo driver and they got translated to MongoQuery we sent the expressions to Entity Framework and they got translated to Sql Server.
I’ve seen a LINQ to REST API provider.
I am however really hoping Amazon provides a MySQL 8.0 compatible version of Aurora with full support for its new hybrid SQL and Document Store interfaces[2] courtesy of the X DevAPI[3] and lightweight "serverless" friendly connections courtesy of the new X Protocol.
That way your don't have to choose just one approach, and you can have your data in one place with high reliability and durability.
My ultimate pipe dream would be that they also provided a redis compatible key/value interface that allows you to fetch simple values directly from the underlying innodb storage engine without going thru the SQL layer, similar to how the memcached plugin currently works[4]
1. https://github.com/wiredtiger/wiredtiger
2. https://mysqlserverteam.com/mysql-8-0-announcing-ga-of-the-m...
3. https://dev.mysql.com/doc/x-devapi-userguide/en/devapi-users...
4. https://dev.mysql.com/doc/refman/8.0/en/innodb-memcached.htm...
Maybe not (but OP makes a lot of good points for why it is), but it is still based on the aurora limits, 64TB of size, 15 low latency read replicas in minutes, and presumably 1 write capacity which makes it a laughable nosql system since it cannot scale past 1 servers write capacity.
X DevAPI and X Protocol/X Plugin could team up and map K/V style access to the server internal InnoDB API instead of using a SQL service as it is currently done. They could try to do it "transparently" or let you set hints. Whatever is desired from an application standpoint.