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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.

HardTechnical
0 practiced
A SaaS business currently pays $2M/year in network egress. Propose architectural and operational tactics that can reduce egress cost by 30%-50% at scale. Consider compression, delta/dedup replication, moving compute to data, CDN adoption, peering/Direct Connect, and multi-cloud trade-offs. Explain how to model ROI and estimate time to recover engineering investment.
HardTechnical
0 practiced
Design disaster recovery options (cold, warm, hot) for a web application that normally handles 1,000 RPS. For each option state the approximate monthly cost drivers (compute, standby storage, data replication, failover testing) and estimate the RTO and RPO. Describe how you would present these options and costs to product leadership with recommendations based on budget and risk tolerance.
MediumTechnical
0 practiced
An analyst ran an ad-hoc query that scanned 2 TB on your analytics cluster and caused a surprise bill spike. Outline a practical action plan to immediately limit further cost impact and medium-term changes to prevent recurrence. Include schema and query-level tactics such as partitioning, clustering, materialized views, query guards, and cost quota controls.
MediumTechnical
0 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?
MediumSystem Design
0 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.

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