In an Amazon SDE 2 interview, system design questions are highly significant because they reveal whether you can think like a software engineer building large-scale, production-ready systems. When interviewers ask about API design, they are not just testing if you can make something work. They want to see if you can create clear, intuitive, and reliable endpoints that a development team can confidently use and maintain. Well-designed APIs should be consistent, easy to understand, and follow best practices so that integration is straightforward and error-free.
Beyond basic functionality, your APIs must handle scale efficiently, stay secure, and operate reliably in real-world scenarios. Considerations like authentication, rate limiting, input validation, and error handling are critical. At the same time, the system should remain maintainable and easy to extend in the future. Interviewers are looking for engineers who combine practical coding skills with thoughtful system design, creating services that are robust, secure, and developer-friendly.
Interview Question
How would you design the APIs for the service?
Question Explanation
This question evaluates your ability to define well-structured, user-friendly APIs that make a service easy to use and integrate. Interviewers want to see how you design endpoints for core actions such as creating short URLs, redirecting users, and managing URLs or user accounts. Your answer should reflect attention to REST principles, request and response formats, error handling, and security, demonstrating practical skills in building scalable and maintainable systems.
Ideal Answer
For a URL shortening service, I would design the APIs around the primary use cases:
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POST /api/shorten: Accepts the original URL and optional fields like expiration time or custom alias. Request body in JSON would include
url,expiration, andalias. Response returns the generated short code and full short URL. -
GET /{shortCode}: Handles redirects. When a user accesses this endpoint, the backend looks up the original URL and responds with a 301 redirect. This endpoint should be optimized for low latency.
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GET /api/urls: Returns all shortened URLs for a user, with pagination if needed.
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DELETE /api/urls/{shortCode}: Allows users to delete their own shortened links.
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GET /api/urls/{shortCode}/stats: Provides analytics such as click counts, timestamps, and breakdowns by location, device, or browser.
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POST /api/keys and DELETE /api/keys/{keyId}: For creating and managing API keys for programmatic access.
For authentication, I would use JWT or OAuth depending on requirements. All input would be validated to prevent abuse or invalid data. The APIs would follow REST principles, consistently use JSON, and be documented with OpenAPI or Swagger for ease of use.
Designing APIs in an Amazon SDE 2 interview goes beyond functionality. It is about creating endpoints that are reliable, maintainable, and easy for developers to use. You must consider scalability, security, error handling, and real-world usability while keeping your design practical.
Practicing system design questions like this helps you gain confidence and improve your approach. Platforms like CareerXcelerator provide hands-on experience with real-world challenges, mock interviews, and guided practice. You learn to design APIs effectively and explain your approach clearly, which is exactly what Amazon expects.
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