> Using a map[int]* Metric instead of a map[string]struct{} would give us that integer key we knew would be faster while keeping access to the strings we needed

> Using a map[int]* Metric instead of a map[string]struct{} would give us that integer key we knew would be faster while keeping access to the strings we needed for the indexes. Indeed, it was much faster: the overall throughput doubled. I'm a little sceptical of this -- type assertions are fast but it's an extra step to initializing a struct. It would have been nice to see tests done comparing map[string]struct{} to map[int]struct{} and comparing map[string]* Metric to map[int]* Metric. Also, there is no way to escape an asterisk, so I apologize for the awkward space after each one.