When using OAuth2, some resources require 'password' grant type and others only need 'client_credentials'. Volos supports both, but a token generated from one grant type would grant access to endpoints and methods protected by the other!
This means that having different grant types in one API is ineffective, because a token generated from any type allows access to all resources in the API.
Since I'm testing with redis now, I thought of hacking the code to force each grant type to use different database. For example, 'password' would use DB0 and 'client_credentials' would use DB1. But there might be a better solution.