How do you integrate this with your existing API? Do you need to proxy requests through Hydra or do you just need to read and trust Hydra-signed tokens on every request? Is there any overlap with https://getkong.org/ ?
You have to query token validation endpoint to have your reference token validated. That's how oauth2 works. With OpenId connect you get JWT which can be validated without a call to the identity provider.
One thing I've not quite got my head around with JWT is not authenticating tokens with the server on each request - am I really just meant to assume a token is trusted until it's expiry time? What if a user signs out all their sessions in the meantime, or an employee is fired and needs access revoking? As far as I can tell I do just have to use short-lived tokens and renew them frequently but that comes with its own set of problems when doing JavaScript based applications and implicit auth.