Options to obtain a client driver
You have two options to develop an application that works with Phoenix, depending on the client-server architecture. They are without PQS and with PQS.
Without Phoenix Query Server:
If your environment does not have a PQS layer, applications that connnect to Phoenix must use the Phoenix JDBC client driver.
With Phoenix Query Server:
PQS is an abstraction layer that enables other languages such as Python and GoLang to work with Phoenix. The layer provides a protocol buffer as an HTTP wrapper around Phoenix JDBC. You might prefer to use a non-Java client driver for one of various reasons, such as to avoid the JVM footprint on the client or to develop with a different application framework.