In its current form, the main use-case is to load data into memory first then serve them through query apis. Thomas has made some effort to support querying data directly from remote source without loading them into memory: https://github.com/roapi/roapi/pull/71. The underlying query engine, Apache Arrow Datafusion, supports running query on data stream on the granularity of partitions. This is not heavily used in roapi at the moment because I want to nail the in memory serving use-case first.