System design
Design a realtime notification system
A system design preview for a high-volume notification product with clear trade-off pressure.
Scenario
Prompt preview
Design a realtime notification system for 50M users across mobile, web, and email channels.
Skills
Skills this rep trains
- Requirements framing
- Fan-out strategy
- Queue design
- Delivery guarantees
- Reliability 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.