Q1
Describe a recent project where you had to optimize code performance. What tools or methods did you use to identify bottlenecks, and what was the measurable improvement?
Why they ask this:* They want to assess your hands-on experience with profiling, debugging, and optimization—critical skills for writing production-quality code at scale.
Q2
Walk us through how you would design a REST API endpoint for a feature you've recently built. What HTTP methods, status codes, and error handling would you include, and why?
Why they ask this:* This tests your understanding of API design principles, RESTful conventions, and practical experience building scalable backend services that integrate with frontend or third-party systems.
Q3
Tell us about a time you had to refactor legacy code or work with an unfamiliar codebase. What was your approach, and how did you ensure you didn't introduce bugs?
Why they ask this:* Mid-level engineers frequently inherit or maintain existing code; they're evaluating your ability to navigate complexity, write tests, and make safe improvements under uncertainty.
Q4
How do you decide whether to use caching in your application, and what caching strategies have you implemented? What trade-offs did you consider?