Cloud Engineer interview question · Most asked
How do you choose between VMs, containers and serverless functions for a new service?
Summary
Consider runtime length and pattern, operational capacity and control needs. Spiky, event-driven, short tasks suit functions; long-running HTTP services and workers suit containers (Cloud Run, ECS on Fargate, Container Apps, or Kubernetes for platforms); VMs fit legacy software, special OS/kernel needs or licensing. Cost depends on utilisation: functions are cheap at low or spiky load, containers/VMs at steady high load.
Longer Answer
Check limits: function timeouts (15 minutes on Lambda), payload sizes, cold starts, and database connection behaviour under high concurrency.
Key Points
- Functions: event-driven, spiky, short.
- Containers: services and workers.
- VMs: special needs.
- Model cost by utilisation.
Deep dive: Cloud Computing Tutorial: Containers in the Cloud
Explanation
What interviewers look for
A structured decision with limits and cost.
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