System design

Design a realtime notification system

A system design preview for a high-volume notification product with clear trade-off pressure.

Practice in the app
Scenario

Prompt preview

Design a realtime notification system for 50M users across mobile, web, and email channels.

Skills this rep trains

Requirements framingFan-out strategyQueue designDelivery guaranteesReliability trade-offs
Rubric preview

How FLOW will score the full answer

The public preview shows what good evidence looks like. The app scores your actual answer and stores the receipt.

Frame: clarifies latency, durability, channel, and user preference requirements.
List: maps fan-out, queueing, storage, retry, and dedupe options.
Optimize: defends the bottleneck and what breaks first at scale.
Follow-ups

Hatch-style coaching prompts

What are the hard latency and durability requirements?
Where do you store notification state?
How do you handle retries and dedupe?
Locked workspace

What unlocks after sign in

Answer workspace with timers, notes, schema or code context where relevant.
Hatch follow-ups that adapt to your weak move instead of giving generic hints.
FLOW score receipts across Frame, List, Optimize, and Win.
Next-drill routing into the career goal you are training for.

Open the full workspace to answer, run, and get scored.

Public previews show the map. The app gives you reps, Hatch follow-ups, FLOW feedback, weak-move drills, and saved proof of progress.

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