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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.

MediumSystem Design
39 practiced
Design a cost-effective architecture for an image processing pipeline that receives 10,000 images/day. Images can be processed within 12 hours (no strict latency). Propose an architecture using either serverless functions, spot worker nodes, or a hybrid. Explain storage choices, queueing, retries, and a simple monthly cost estimation approach where you state assumptions.
EasyTechnical
40 practiced
Explain how serverless compute (for example AWS Lambda) changes cost characteristics compared to always-on VMs: what are the main billing axes to monitor, how do function memory and execution time affect cost, and what operational patterns can inadvertently increase cost (for example: excessive cold starts, high concurrency).
MediumTechnical
39 practiced
Explain how spot/preemptible instances work and list practical architectural patterns to mitigate interruptions for batch processing, stream processing, and ephemeral web workers. For each pattern, describe the trade-offs in cost and complexity.
MediumTechnical
38 practiced
Describe an Infrastructure-as-Code pattern to reduce cloud spend during off-hours for development and staging environments using Terraform (or similar). What resources can safely be stopped or scaled to zero, what should not be destroyed, and how would you schedule and automate this with minimal developer friction?
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.

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