Interview Simulator · System Design
Design a News Feed
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 the home timeline for a Twitter-like service. It has 500 million users, about 200 million of them active each day, and the average account follows 200 others. Timeline reads have to return in under 200 ms at p95, and new tweets should reach followers within a few seconds.