2 · Core infrastructure

4. Compute: Instances, Autoscaling and Placement

Instance families, purchase options, scaling policies and availability design.

10 min read · 3 MCQs

Choosing compute

Instance families are tuned for general purpose, compute, memory, storage or GPU workloads. Right-sizing from real utilisation data is the single biggest cost lever most teams never pull.

Purchase options

On-demand is flexible and expensive. Reserved instances and savings plans trade a one- to three-year commitment for large discounts. Spot/preemptible capacity is up to 90% cheaper but can be reclaimed with a short warning, so it suits stateless, checkpointed or batch work.

Scaling and availability

Horizontal scaling adds instances behind a load balancer and is the cloud-native default; vertical scaling grows one machine and eventually hits a ceiling. Spread instances across availability zones, and use regions for disaster recovery and data residency.

  • Scale on a leading signal (queue depth, RPS), not just CPU.
  • Set sane cooldowns to avoid thrashing.
  • Health checks must fail fast and honestly.

Chapter quiz

3 questions · pass mark 75%
  1. 1. Spot instances are appropriate for…

  2. 2. Availability zones exist to isolate…

  3. 3. The cloud-native default scaling approach is…

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