Practice tools
Reading is not enough for an interview. These tools let you change one thing and see what happens. Each tool belongs to a case study. Every tool works with the keyboard. Nothing is saved and nothing leaves your browser.
The 4 tools
- Practice timerA 45-minute clock for a mobile system design round, with a prompt, five steps and a checklist.
- Case
- All case studies
- You
- Run a timed round
- Without JavaScript
- A table of examples
- Saved
- Nothing
- Retry explorerChange the retry rules and see if a lost reply makes a duplicate message.
- Case
- Chat app
- You
- Change settings, press run
- Without JavaScript
- A table of examples
- Saved
- Nothing
- Pagination raceChange one thing and watch a list repeat or miss posts. Compare page numbers with a cursor.
- You
- Press buttons, watch two lists
- Without JavaScript
- A table of examples
- Saved
- Nothing
- Offline chat simulatorSend a chat message with no connection and lose a reply. Watch the outbox and the server.
- Case
- Chat app
- You
- Press three buttons, watch three panes
- Without JavaScript
- A table of examples
- Saved
- Nothing
How these tools work
Each tool is a small model that runs in your browser. It gives the same result every time for the same steps. The model is simpler than a real app. Each page lists what it leaves out.
If JavaScript is off, each page still shows a plain explanation and a table of examples. Not sure where to begin? Pick a reading path for your level.
Get the free one-page cheat sheet
One page: the five steps, a 45-minute time plan and two checklists. Print it or keep it on your phone.
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