Experience how real interviewers probe your decisions with follow-ups, curveballs, and coding challenges. Build the reasoning skills that get you hired.
Follow-ups expose consequences naturally, just like a real interview.
Numeric scores for architecture, scale, tradeoffs, and more.
Revise your first answer after discovering what breaks at scale.
Optional countdown timer for realistic interview pressure.
Choose a real-time communication strategy and discover what breaks at scale.
Millions of fans watching live scores that update every few seconds. Polling, SSE, or WebSocket — and what happens when a goal is scored?
Every keystroke triggers an API call. How do you tame the request storm while keeping results instant?
Millions of posts, paginated API, and the user scrolls fast. How do you keep the feed smooth, correct, and memory-efficient?
You need to upload 200 images. Fire all at once and the browser tabs out. Fire sequentially and it takes 10 minutes. What's the right concurrency?
The user clicks 'Like' and sees instant feedback. But the server rejected it. What happens next?
Notifications from 5 different sources, each with different priorities. How do you design the client-side pub/sub layer?
User logs out in one tab but stays logged in another. How do you keep tabs in sync?