Redis will be faster than Postgres because Pg offers reliability guarantees on your data (when the transaction is committed, it is guaranteed to be on disk), whereas Redis has a concept of writing to disk when it feels like it, so shouldn’t be used for critical data.
Redis seems like a good option for your session data, or heck even store in a cookie or in your client side Javascript. But if you need data from your database on every request then it might not be even worth involving Redis. It very much depends on your application.