How to validate Oauth token in datacenter ?

I have setup OAuth in my application but unable to check whether token is expired or not.

In current implementation i’m storing access token in my application db but no way to validate it.

I’ve gone through the API list provided to implement searching repositories based on repo name but only public repo are listed since search repositories can be also accessed without token.

I’m expecting the above behaviour from API: If the token is expired instead of processing the request with HTTP status code 200 , I need to return 401 (unauthorised).

Response: with invalid or tampered token.

Response: with valid token.