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tliao

In terms of reliability, this is a much better scheme than the previous one where each worker had to maintain state. Now, if a worker were to go down for any reason, the load balancer can easily have assign another worker to the user without having to create a new session. This does produce some problems though since the database is now the point of contention.

fangyihua

Some trade off will always be required. The stateless design does not come without a cost. If you desire reliability and robustness, then be ready to sacrifice some performance.

yingchal

Database here is used to persistent session information and makes server stateless, which makes load balancer a lot easier to do their work. From the point of recovery if server crashes, stateless server also results in faster recovery phase. To reduce the contention of database, I think each server can hold session information as lease for a certain time instead of contacting DB constantly.