Try libeatmydata in edx-platform tests
libeatmydata speeds up disk writes by turning off fsync functionality; this increases the risk of data loss on crashes, but this is a negligible risk when running tests (crashes are rare and typically cause the tests to fail anyway).
Review New Relic Infrastructure metrics to identify the processes which write the most data to disk during edx-platform test jobs (npm, pip, MySQL, and MongoDB are likely candidates).
Install libeatmydata on the AMIs used to run tests
Try enabling libeatmydata for the target processes and measure the impact (if any) on job duration.