Cost Aware Architecture and Design Questions

Focuses on how architectural decisions and design patterns affect operating cost and total cost of ownership. Interviewees should be able to reason about trade offs such as managed services versus self managed components, always on virtual machines versus event driven or serverless approaches, reserved versus on demand capacity, use of spot or preemptible instances, and multi region or edge placement. Candidates should demonstrate techniques for reducing cost through storage class selection and lifecycle policies, caching and batching, query and workload optimization, data transfer minimization, and workload isolation. The topic also covers modeling and communicating cost trade offs, estimating ongoing operating expense for alternative designs, and choosing architecture that balances budget constraints with reliability, performance, and engineering effort.

EasyTechnical

35 practiced

Explain what cost-aware architecture means in cloud and infrastructure contexts. Describe three concrete ways architectural choices (for example: managed vs self-managed components; always-on VMs vs serverless/event-driven; storage class selection and lifecycle policies) affect ongoing operating cost and total cost of ownership for a typical web application. For each way, give a short example change, the expected direction of cost impact (increase/decrease) and the main engineering trade-offs you would consider.

EasyTechnical

35 practiced

You run a stateful service on an autoscaling group with reserved instance commitments covering 60% of baseline capacity. Explain simple heuristics to decide how much additional capacity to keep as buffer (headroom) for traffic spikes versus minimizing cost. What metrics and historical analyses would you use to set that buffer?

HardTechnical

39 practiced

Your analytics workload is on BigQuery and a common report scans an entire 10 TB table each run. Show concrete schema and query-level changes (for example: partitioning, clustering, rewriting the SQL, materialized views) that reduce bytes scanned by at least 90%. Provide example SQL snippets and explain why they reduce cost.

HardTechnical

36 practiced

Leadership scenario: You are the tech lead and have been told infrastructure budget must be cut by 30% next year. Describe a prioritized 90-day plan to identify and implement 30% cost reductions without violating critical SLAs. Include quick wins, medium-term projects, required stakeholder communications, and how you would measure and report progress.

MediumTechnical

55 practiced

Explain how to run mixed-priority workloads on Kubernetes while minimizing cost. Include node pools (on-demand vs spot), taints/tolerations, priority classes, pod disruption budgets, and how to schedule background batch jobs to use spare capacity without impacting critical services.

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