Apache Calcite / Java developer

We're looking for someone experienced with Apache Calcite. We are developing a low code platform that needs to provide the facility to query data across multiple data sources (Data Virtualization) such as SQL databases, REST services, and NoSQL databases. We see Apache Calcite as a potential solution for that. We are looking for someone that has deep experience with Apache Calcite to develop a POC. The POC should demonstrate the following: -Single query that can talk to multiple SQL data sources such as mysql and postgres and REST. -Wherever possible it should pushdown filters and joins to the underlying data sources instead of letting Calcite do it in memory. -Existing Calcite Adapter needs to be tweaked and new optimization rules need to be developed. -Explain some intricacies of Calcite to our team.