Hey hanan. It depends what you want to keep from your monolith, or which other microservices you want to use. If you are looking for a full auth solution, I would of course recommend the whole Ory stack:

• Ory Hydra is an OAuth 2.0 and OpenID Connect provider.
• Ory Oathkeeper is an Identity and Access Proxy.
• Ory Keto is an access control server.
• Ory Kratos is an identity management server.

But you can always pick and choose, so for example just use Ory Oathkeeper and Ory Hydra for securing endpoints and managing OAuth2, or just Ory Kratos to manage your users, ect.

Feel free to join our slack or the Github Discussions (kratos or hydra would be best in your case i presume). Most of our community you will find there!