Thanks! One of the creators here. Our main idea with Lavastone is that you just write “plain” c++ code that doesn’t call any special query interface. It’s transparently making your code run by performing some interactions with the database on your behalf. In this sense the query interface looks just like the standard language features of C++.

As you point out, there are definitely trade offs with choosing Lavastone instead of a SQL database. For instance you can’t easily share concurrent read/write access to the same Lavastone data with multiple processes. However, you can copy a fixed Lavastone data store (ie the underlying LevelDB store) and distribute it to multiple server nodes. That’s how we used it anyways!