From what I can gather, Registry is a way to localize keys to make using OTP stuff a bit easier. This is especially important when you want to use a binary key for a GenServer or Agent instead of an atom or setting it to {:global, key}.

That said, and I’m chalking this up to my own ignorance, it seems to be HIGHLY unintuitive to use. In my mind Registry is basically a supervised key/value store (like a map, but backed by an ets table) where the key responds to a {pid, init_value} tuple (or list of tuples if :duplicate is used). So when we have a function called keys, it makes sense that I’m looking for the keys within that Registry, especially since Registry.count/1 takes in the name of the Registry and returns the number of keys… Instead, we’re expected to also pass along the pid, to get the key(s) associated with it? If I’m using Registry as a way to make GenServer or Agent easier to use (not having to know the pid to pass along), why do I need to know the pid to pass along?

Similarly, Registry.values requires the registry name, a pid, AND the key? Does Map.values/1 require anything other than the map?

I understand there needs to be a difference in usages based on :unique vs :duplicate, but that seems like it could be solved via pattern matching. I like the idea of Registry, but it seems VERY clunky to use for what it’s trying to do. Am I just super ignorant of the underlying mechanisms? If so, I’d love some clarification so I can better understand where I’m falling short.