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AI mock interview for Backend Developers
APIs, databases, concurrency and reliability — practice explaining backend trade-offs out loud and see exactly where your reasoning got thin.
Free 10-minute interview with a full report. Paid plans run full-length sessions.
Backend Developer interview questions you might get
A sample of the starting questions. The live interview follows up on your answer, so no two sessions go the same way.
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Design a payments endpoint that a mobile client may call twice on a flaky network. How do you avoid charging twice?
What it tests: Idempotency keys and exactly-once thinking.
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A query that took 20 ms now takes 4 seconds. Walk me through how you diagnose it.
What it tests: Indexes, query plans and data growth.
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Two workers process the same job from a queue. What went wrong and how do you prevent it?
What it tests: At-least-once delivery and locking.
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When would you put Redis in front of your database, and what breaks when you do?
What it tests: Cache invalidation and consistency.
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Describe the most painful outage you were part of. What did you change afterwards?
What it tests: Ownership and operational maturity.
How a session works
About 20–30 minutes from setup to report. End any time and you still get feedback on what was covered.
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Set your target
Pick a role, level and stack. Add a job description or your resume if you want questions about your real projects.
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Answer live
Speak or type. The interviewer follows up on thin answers, raises the difficulty when you're doing well and switches to code when it fits.
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Read the notes
A report scores every competency, quotes the answers that cost you, and gives you a prep plan for the next session.
A report that quotes you, not a pat on the back
Every score links back to something you actually said.
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Competency scores
Weighted to the role you picked, so a system design gap counts more for a senior backend role than for a frontend junior.
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STAR check on every story
See which part of each behavioral answer was missing — usually the Result.
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How you sounded
Filler words, hedging, "I" versus "we", and whether you cited real numbers — measured from your words, and compared between the first and second half of the interview.
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A prep plan
The two or three things to practice next, and a skill graph that tracks them across sessions.
Competencies — sample report
STAR — "Tell me about a missed deadline"
How you sounded
Questions
Which languages are supported?
Any. Backend questions focus on design and reasoning; coding questions accept the language you name, such as Java, Python, Go, C# or Node.js.
Does it cover system design?
Mid and senior backend sessions include design questions. For a dedicated design round, use the System Design interviewer.
How is my answer scored?
Each answer is scored against weighted competencies. Deterministic language analysis runs alongside the AI's judgment, and the AI can only nudge scores within a bounded range.
Is it free to try?
Yes. Each month you get a free interview of up to 10 minutes with its scored report. Paid plans add full-length interviews, every track and the full 360 report.