Interview Simulator · System Design
Design a File Sync Service
A full 45 minute round, one phase at a time. Each phase has a time budget, follow-up questions from the interviewer, and a checklist for your level. Reveal a phase's model answer whenever you need it; the report shows which phases you earned.
Design a file sync service like Dropbox. It has 100 million daily users who each change about 10 files a day across several devices. Uploads resume after a dropped connection, identical data is stored once, and no edit is silently lost when two devices change the same file.