Load Balancing and Auto Scaling Questions and Answers

Answer: A

Most real systems combine several, with a schedule for the known pattern and a reactive policy for what the schedule did not anticipate. Relying on one alone is usually a mistake. The schedule handles the known load and the reactive policy handles the surprise.

Answer: B

The cost of being slightly overprovisioned is small and predictable, while the cost of being short is an outage. Asymmetric thresholds are the usual arrangement. Being a little overprovisioned is a cost; being underprovisioned is an incident.

Answer: C

Both are true and the reason gives the asymmetry of the risks, and it also happens to reduce flapping by widening the band between the two actions. One adjustment therefore addresses both the risk and the oscillation together.

Answer: D

Files on a local disk are visible to one instance only and lost when it is replaced. The other three all remove state from the instance where it would prevent scaling. Object storage is the usual destination for the uploads in the fourth option.

Answer: A

A shared database, a lock or a network path eventually becomes the constraint. Finding what saturates first is the whole business of scalability testing. The answer is rarely the component anyone expected before the test was run.

Answer: B

Both are true and the reason gives the mechanism, and the remedy lies in the shared resource rather than in adding yet more instances, which only increase the contention for it. Sharding, caching or a read replica addresses the cause where more instances cannot.

Answer: C

Adding instances without knowing what saturates is guesswork and often makes a shared bottleneck worse. The verification step is what confirms the diagnosis was right. Skipping it leaves you unable to say whether the change helped or merely coincided.

Answer: D

The first two are correct. The third is not so, since shared bottlenecks often appear only at scale and a small environment may show none of them. A test environment a tenth the size can be actively misleading about the limit.