Calcite is actually pretty damn fast, the overhead is surprisingly minimal. I am using it as the backbone for my hobby project that auto-generated federated Gr

Calcite is actually pretty damn fast, the overhead is surprisingly minimal. I am using it as the backbone for my hobby project that auto-generated federated GraphQL API's: https://github.com/GavinRay97/GraphQLCalcite https://github.com/GavinRay97/GraphQLCalcite The experience has been incredibly positive and the community has been incredibly helpful & supportive. It's one of the coolest technical projects I've ever seen and has sparked my interest in query engines and relational databases. I posted some JMH benchmarks of an app that parses a GraphQL query, converts it to Calcite relational expressions, and then executes it against an in-memory DB and it ran on the orders of milliseconds: https://lists.apache.org/thread/hofjx628864t0kt4kk8vo4tjfrxbqf7o https://lists.apache.org/thread/hofjx628864t0kt4kk8vo4tjfrxb... Something very similar to Calcite but much lesser-known is the "Teiid" project: https://github.com/teiid/teiid https://github.com/teiid/teiid Highly recommend checking the code out. It's got a brilliant query optimizer/planner tailored to cross-datasource queries, a cache system, and a translator architecture that can convert a generic SQL dialect to dozens of SQL/NoSQL flavors. Also integrates other data sources like REST API's, S3, flat files etc as queryable data sources.