Read Receipts

What would you ask before drawing a single box?

Ambiguity you would resolve with the interviewer: scope, scale, who uses it, what counts as done.

About Read Receipts

Per-message per-recipient. Group chat amplifies.

Difficulty
intermediate
Time
about 50 minutes
Stages
10
Topic
Real-Time: Chat, Presence & Live Updates

How this problem is worked

Ten stages, from the questions you would ask an interviewer to the trade-offs you would defend. Each asks one question, and the simulator runs the architecture you draw against the requirements you wrote.

  1. 01ClarificationsWhat would you ask before drawing a single box?
  2. 02Functional reqsWhat must this system actually do?
  3. 03Non-functionalWhat must it promise about speed, uptime and correctness?
  4. 04Capacity estimationHow much load and data does this have to hold?
  5. 05API designWhat does the outside world call, and what comes back?
  6. 06Data modelWhat gets stored, and what is it looked up by?
  7. 07Use-case breakdownHow does each requirement actually get served?
  8. 08High-level designWhich components handle a request, and in what order?
  9. 09Deep divesWhich part breaks first, and what do you do about it?
  10. 10Trade-offsWhat did this design cost, and what breaks at 10×?

More in Real-Time: Chat, Presence & Live Updates

Long-lived connections and the things you push down them — messages, cursors, green dots, scores, prices and bids.

Browse the full problem catalog, or see what the simulator does and does not model.