Running every two minutes sounds pretty deterministic.

It was perhaps too deterministic. What's not mentioned in the blog is that after running for long enough, the cluster would line up it's GCs, and each node would do the 2 minute GC at exactly the same time causing bigger spikes as the entire cluster would degrade. I'm guessing all it takes is a few day night cycles combined with a spike in traffic to make all the nodes reset their forced GC timers to the same time.

Interesting, sounds like 2 minutes + random fuzz might avoid the thundering herd. Might be worth submitting a patch to the golang team!