Suppose we have a load balancer with 3 instances.
1. A section, s1, is created in instance 1 for a given app.
2. There is a network issue. instance 1 is not available in the network.
3. Subsequent requests go to instance 2.
4. The session, s1, in instance 1 is still in memory and will be expired, and then removed.
This will cause an issue.
The same issue is in HA SSO.