Currently Composer supports only static sharding which is a feature of Android Test Support library.

Static sharding tend to be inefficient since it is impossible to know statically duration of each individual test execution, which means that some devices may run out of tests to execute faster than others which creates bottleneck for the overall test run time.

Composer can communicate with test runner on a device and run tests in interactive mode when Composer gives commands to test runner on a device to run particular test which should decrease overall test run time and increase resource usage efficiency.