The Phoenix Query Server API documentation can be found on the Apache Calcite website. PQS is essentially a branding of the Avatica Server.
https://calcite.apache.org/avatica/docs/protobuf_reference.html The write performance of the Thin Driver with PQS is very close to the performance of the Thick driver as long as you as the client is using the batch-oriented APIs to write data (https://calcite.apache.org/avatica/docs/protobuf_reference.html#prepareandexecutebatchrequest). These map to the executeBatch() API calls on PreparedStatement. I have done performance evaluation which showed that, when using these API calls, performance between thick and thin is roughly equivalent. Non-batch API calls through the thin driver were roughly 30% slower than the thick driver. On the read side, I have not noticed any discernible difference in the performance between the two approaches. Overall, the thick driver is likely going to perform better than the thin driver because it has to do less work, but the gap is small. Depending on the physical deployment of your application, deploying multiple PQS instances on "beefier" server nodes than lightweight "edge" nodes, the thin driver might result in better overall performance.
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