IdentityServer4-MongoDB-Sample
Implementation of IdentityServer4 with MongoDB backing. I've used the sample solution from https://github.com/IdentityServer/IdentityServer4.Samples/tree/master/Mvc as a starting point and replaced the in-memory version of the user store and client store with stores backed by MongoDB.
Blog post
I've also written a blog post about this implementation: http://blog.stoverud.no/posts/identity-server-with-mongodb/