Hi a question, how can you avoid duplicate logins with Phalcon? If a user already logged in, you can not enter this user until closing session
store session data in your database and you should have some backend job to check that user is keepalive . try this https://stackoverflow.com/questions/38043015/tell-if-http-request-is-keep-alive
With high concurrency, you'd better use (lib)Memcached.
Incubator
No, you don't need Incubator for that.
For both Phalcon 2.x and 3.x you have libmemcached session adapter:
https://docs.phalcon.io/en/latest/api/Phalcon_Session_Adapter_Libmemcached.html