This is about spot on. I do get the part about testability, but with a simple Key/Value use case like this, BoltDB or Pebble might have fit extremely well into

This is about spot on. I do get the part about testability, but with a simple Key/Value use case like this, BoltDB or Pebble might have fit extremely well into the Native Golang paradigm as a backing store for the in-memory maps while not needing nearly as much custom code. Plus maybe replacing the sync.Mutex with RWMutexes for optimum read performance in a seldom-write use case. On the other hand again, I feel a bit weird criticizing Brad Fitzpatrick ;-) — so there might be other things at play I don‘t have a clue about...