[nasretdinov]

It potentially still might make a difference due to reduced contention: if we have more shards the chances of two or more goroutines hitting the same shard would be lower. In my mind the only downside to having more shards is the upfront cost, so it might slow down the smallest example only

[kgeist]

The upfront cost isn't that big: a Go map+RW lock is probably a few hundred bytes. Allocating them costs far below 1 ms.