Nothing's difficult about that. But that doesn't mean that it's a good idea. How about distributing a signature and encryption key to all your servers, and using them to secure the outgoing and verify the incoming tokens. If you want easy, that's probably even easier than setting up a Redis store and tying your services to it.

Need an emergency revoke of every token? Easy: Replace your signature key. Any older token will fail signature verification. In which case, your system should require authentication and then generate a new token with an updated signature.