Backend Engineering

API Design

15 practice questions. Free questions open a full answer guide; the rest unlock with Pro.

  • Walk me through how you would debug a production issue where an API endpoint is returning 500 errors for roughly 10% of requests. Mid level
  • How would you make a payment or order-creation API endpoint safe to retry without double-charging the customer?Go Pro Mid level
  • What does it mean for an HTTP method to be idempotent, and how does that shape how you design an API that clients might retry?Go Pro Junior level
  • How would you decide between offset-based and cursor-based pagination when designing a list endpoint, and what are the trade-offs?Go Pro Junior level
  • What are the trade-offs between REST and GraphQL for an API used by multiple client types (mobile, web, third-party)?Go Pro Mid level
  • How do you decide when technical debt is worth paying down now versus later?Go Pro Mid level
  • Describe a time you had to refactor a messy piece of code while the feature was still in use. How did you manage the risk?Go Pro Mid level
  • How do you raise the technical level of the engineers around you, especially those more junior than you?Go Pro Senior level
  • How do you evolve an API that other teams depend on without breaking their integrations?Go Pro Mid level
  • How do you ramp up on a large, unfamiliar codebase quickly without breaking things?Go Pro Senior level
  • Describe a time your technical assumptions were wrong in a significant way. What happened and what did you learn?Go Pro Senior level
  • How do you approach code review — both giving and receiving feedback?Go Pro Mid level
  • How do you decide when to pay down technical debt versus continuing to ship features, and how do you make that case to the rest of the team?Go Pro Senior level
  • How do you handle disagreements with a product manager or engineering manager about technical scope or timelines?Go Pro Senior level
  • How do you approach making a technology choice that will affect your team for years? Walk me through your decision-making process.Go Pro Senior level
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