MobileSD
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Practice mobile system design interviews.

A free guide for senior mobile engineers preparing for interviews. Read short chapters, try practice questions, and learn from real bugs that have shipped to production.

01 · Practice

Eight ways to rehearse.

All free, all included, all repeatable. Pick whichever feels weakest.

02 · How it works

Three things you can do.

Use any of them, in any order. There's no required path.

03 · What's inside

13 chapters. One sample question.

Browse the full list, or peek at the kind of question you'll work through.

All chapters~12 hours total
Sample question

A user makes a few edits in a notes app while offline. When they reconnect, some edits are missing. How would you design a more reliable sync?

Walk through what you'd ask, what you'd build, and the tradeoffs you'd weigh.

You getA clear prompt and 3 hints if you get stuck.
ThenA sample answer plus what an interviewer is listening for.
FinallyA short list of follow-ups they might ask next.
04 · Real bugs

Things that have actually broken in production.

Each one is a short story with a question — try to figure out what went wrong before reading the answer.

+ 25 more bugs in the full library
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Ready when you are.

Pick up anywhere. Your progress saves automatically.