System Design · Middle · Question 72 of 75

Why can sticky sessions on a load balancer cause problems?

✓Correct answer: Load becomes uneven and users lose their session when their server dies; storing session state externally avoids this
2They make HTTPS impossible
3They break caching headers

Explanation

Stateless app servers (state in Redis/database/token) can be added, removed and restarted freely.

Further reading

Wikipedia: Load balancing ↗

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