System design interview practice, with an AI verdict

Walk into your system-design interview ready.

Practice the exact designs top companies ask, guided step by step, with AI feedback on every answer and a simulated hiring verdict when you finish.

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22 real problems · 34 lessons · 8 tracks · English & Bahasa Indonesia

Practice like the real thing

Not passive reading. You work each design end to end, clarify requirements, do the capacity math, define APIs, draw the architecture, and go deep, exactly the arc of a real interview.

Graded like an interviewer

An AI interviewer reads what you actually wrote, gives specific, actionable feedback per step, and returns a simulated hire to no-hire verdict, the way real interviewers weigh signal.

Build the fundamentals

The mental models behind every strong answer: scaling, storage, caching, messaging, consistency, and the behavioral round, in short focused lessons.

How it works

1

Pick a design

Choose from real problems, from URL Shortener to Uber, Twitter and YouTube, sorted by difficulty.

2

Work it step by step

Requirements, capacity math, API design, architecture and deep dives. Sketch your system on the built-in diagram canvas.

3

Get AI feedback

Specific notes on what you did well and exactly what a strong answer would add, on any step you want.

4

See your verdict

A simulated Strong Hire to No Hire signal with a full breakdown, so you can track your prep over time.

What's inside

All problems ›
Starter
Starter
Design Comment System
Thread millions of comments under hot posts, keep reads fast, and stop spam from flooding the timeline.
Starter
Starter
Design Pastebin
Store and serve arbitrary text blobs at scale with expiry, and decide what belongs in blob storage versus a database.
Starter
Starter
Design Rate Limiter
Decide allow-or-reject for every request in a millisecond with token buckets, sliding windows, and distributed counters.
Starter
Starter
Design URL Shortener
Turn billions of long URLs into short codes and redirect them in under 50ms, without collisions.
Intermediate
Intermediate
Design Dropbox
Sync files across devices with chunking and dedup, and resolve conflicts when two edits collide.
Intermediate
Intermediate
Design Google Calendar
Model events, recurrence, and invites, and detect scheduling conflicts across time zones.
Intermediate
Intermediate
Design LeetCode
Run untrusted code safely in sandboxes and judge submissions against test cases at scale.
Intermediate
Intermediate
Design Tinder
Swipe, match, and recommend at scale, with geospatial sharding and the double-opt-in 'it's a match' problem.
Intermediate
Intermediate
Design Typeahead Suggestion
Return search suggestions in under 100ms as the user types, using tries, caching, and ranking by popularity.
Intermediate
Intermediate
Design Webhook Delivery System
Deliver events reliably to third-party endpoints with retries, backoff, ordering, and at-least-once guarantees.
Advanced
Advanced
Design Google Maps
Store the planet's road network and compute shortest paths across a graph with billions of edges.
Advanced
Advanced
Design Spotify Top-K
Find the top-K trending tracks over a stream of billions of plays without storing every event.
Advanced
Advanced
Design Ticketmaster
Sell limited seats to a stampede of buyers without overselling, using holds, locking, and fairness.
Advanced
Advanced
Design Twitter
Fan out tweets to millions of followers, and solve the celebrity problem that breaks the naive design.
Advanced
Advanced
Design Uber
Match riders to nearby drivers in real time with geospatial indexing and live location updates.
Advanced
Advanced
Design WhatsApp
Deliver messages instantly with read receipts, presence, and ordering across a user's devices.
Advanced
Advanced
Design Yelp
Search millions of businesses by location and rating with geospatial indexes and read-heavy caching.
Advanced
Advanced
Design YouTube
Ingest, transcode, and stream video to a global audience with a CDN and adaptive bitrate.
Expert
Expert
Design Collaborative Editing
Let many people edit one document live, using CRDTs or OT for conflict-free convergence.
Expert
Expert
Design Distributed Message Queue
Build the queue everyone else depends on, with partitioning, ordering, and durable delivery.
Expert
Expert
Design Job Scheduler
Run millions of jobs at the right time with retries, idempotency, and exactly-once semantics.
Expert
Expert
Design Realtime Monitoring
Ingest a firehose of metrics, aggregate over time windows, and alert the moment SLOs burn.

Questions

Do I need an account?

Sign in with Google to save your attempts, feedback and verdicts. It's one click, no password.

How are my answers graded?

An AI interviewer reads each step and your whole design against a rubric, gives specific feedback, and returns a simulated hire / no-hire verdict. It's a signal to guide your prep, not a real hiring decision.

What will I practice?

22 real system-design problems plus 34 fundamentals lessons across 8 tracks.

Is it available in my language?

Lessons and problems are available in English and Bahasa Indonesia. Switch anytime from the top bar.

Ready to design like the top 1%?

Start with a single problem today.

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