Question: Everything was working fine. All of a sudden, people are complaining that they keep getting logged out in few seconds after login

Answer: Redis is fill or is giving errors. Check gate-logs, and search for "jedis" errors. Other errors could be misleading e.g. "Authenticated user not present in authentication", a common issue with Fiat does not have groups associated with the logged-in user. In this case, as Redis is full, Fiat is unable to store the groups for users.