This is a very bad idea. You cannot hide ETL in a Rest API, at most you can hide the T part and it's a lot more work. you need to build an extra service that reads the data from a database and does some padgination. It's way more complex than a one-liner to get data from a jdbc connection and way much slower.

I like the way how it buffers messages. You basically stop a process and it will continue when it left off. It is easy to create a distributed cluster. It has hundreds of different connectors for external sources. On the other hand is very bulky. Making it to work with https was horrible. You cannot just put it behind a reverse proxy.