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HardPrep Room Coding #3804

Push notification gateway

System designNetworking & APIsDistributed systemsSenior–Staff~45 min

Design a push-notification gateway that delivers to 300M devices across APNs (iOS) and FCM (Android) at a peak burst of 1M notifications/sec (e.g. a breaking-news fan-out). You must respect provider connection limits and rate limits, dedupe, handle invalid/expired device tokens, and give product teams accurate delivery feedback. What does the pipeline look like and what's the hard part?

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.

Clarify5:00 left
Estimate5:00 planned
Design15:00 planned
Deep dive12:00 planned
Failure8:00 planned
0:00
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.