Performance Engineering and Cost Optimization Questions

Engineering practices and trade offs for meeting performance objectives while controlling operational cost. Topics include setting latency and throughput targets and latency budgets; benchmarking profiling and tuning across application database and infrastructure layers; memory compute serialization and batching optimizations; asynchronous processing and workload shaping; capacity estimation and right sizing for compute and storage to reduce cost; understanding cost drivers in cloud environments including network egress and storage tiering; trade offs between real time and batch processing; and monitoring to detect and prevent performance regressions. Candidates should describe measurement driven approaches to optimization and be able to justify trade offs between cost complexity and user experience.

MediumSystem Design

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Design a throttling and rate-limiting policy for a public API that protects backend systems while minimizing user friction. Explain where to enforce limits (edge, gateway, service), token bucket versus leaky bucket considerations, differentiation by user tier, and how to measure the policy's effectiveness post-launch.

HardTechnical

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You are asked to build a cost allocation model for a multi-region product that uses different storage tiers and has substantial egress. Describe a practical approach to attribute costs to product lines and features, what tagging and data you need from engineering, and how you would present results so product leads can make optimization decisions.

HardTechnical

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A production service occasionally runs out of memory and causes crashes. Outline the communication plan to internal stakeholders and customers, immediate mitigation steps to reduce customer impact, the triage and root cause approach you would require from engineering, and what longer term roadmap changes might be required to prevent recurrence.

MediumTechnical

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You need to define what constitutes a performance regression in production for a customer-facing service. Describe the SLIs, thresholds, statistical methods, and alerting strategy you would use to distinguish signal from noise and avoid alert fatigue while still catching real regressions.

MediumTechnical

0 practiced

Design a dashboard template for product managers to track performance and cost for a live product. List 8-10 panels or charts you would include, who owns each metric, alert thresholds, and how you would use the dashboard for weekly roadmap decisions.

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