Backend Engineering
Performance & Scaling
5 practice questions. Free questions open a full answer guide; the rest unlock with Pro.
- If someone reports your API 'feels slow,' why is the average response time often a misleading number, and what would you look at instead?
- Your backend service is hitting its limits under growing traffic. Walk me through how you'd decide between scaling it up versus scaling it out, and what has to be true about the service for scaling out to actually work.Go Pro
- A user-facing endpoint fans out to several internal services in parallel and waits for all of them. Each downstream service reports a healthy p99, yet the endpoint's own p99 is far worse than any single dependency. Explain why this happens and what you'd do about it.Go Pro
- Under a sudden traffic spike, your service's latency climbs, requests queue up, and autoscaling hasn't added capacity fast enough — and clients start retrying, which makes it worse. How would you design the service to stay up and recover during a spike like this instead of collapsing?Go Pro
- What's the difference between scaling a service horizontally and vertically, and why does horizontal scaling usually require the service to be stateless?Go Pro
Want questions matched to your role? Paste a job title, job description, or CV for a personalized set, or go Pro to unlock the full bank.