You should consider switching to window.performance.now() as that is a monotonically increasing clock, instead of a wall clock that might randomly be adjusted w

You should consider switching to window.performance.now() as that is a monotonically increasing clock, instead of a wall clock that might randomly be adjusted with time sync services. Also, maybe you should run the tests in sequence instead of at the same time. I wonder if running two concurrent fetches might disadvantage the second fetch?