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Handle traffic spikes and estimate server capacity

HeadwaySoftware Engineer · Technical Screen
MediumSoftware EngineerTechnical ScreenSystem Design

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This question evaluates a candidate's competency in performance troubleshooting, capacity planning, and scalable system architecture, focusing on diagnosing overload causes and quantifying infrastructure needs.

Scenario

You are designing and operating a backend service that receives API requests from clients. Recently, the service becomes slow or times out when request volume spikes.

Questions

  1. Too many requests cause the server to slow down. What would you do to diagnose and mitigate the issue?
  • Assume you can change both infrastructure and application code.
  • Discuss both immediate mitigations and longer-term architectural changes.
  1. Given a set of assumptions (users, request rates, data volume), how would you estimate required server capacity?
  • Explain what inputs you need (traffic, latency/SLO, CPU/memory per request, storage growth, peak-to-average factor, etc.).
  • Provide a method to translate those assumptions into numbers of instances, database capacity, and network/storage needs.