Unfortunately it has a major issue

[lmattcris]

It all would work, only if it wasn't for this
https://failingfast.io/erratic-behaviour-from-net-memorycache-expiration/

The MemoryCache is expiring only on 20-seconds boundaries (like 12:34:00, 12:34:20, 12:34:40, ...). Then every event in between won't be recognized for up to 20 seconds - which is pretty unusable, to be responsive.