Should I keep my Session Management on PostgreSQL or an external cache mechanism like Redis or Memcached?

With long and painful researches i decided to use session based authentication. I am developing an Web application with .Net core as backend and React js as frontend. I recently swap Node js backend to .Net Core. I am using PostgreSQL as my database. I heard PostgreSQL is bad for keeping sessions in it because it will be slow after like 10.000 session because it doesn’t use cache and queries will be problem. Then i read How to Boost PostgreSQL Cache Performance and learn PostgreSQL also has a caching mechanism and it’s managable. I can’t decide which way to go. Also i read using Redis in production is not allowed, so its not free i guess? Can you help me decide? Thank you.