System Design

Push Alerts to 10M Devices Under 60s

System Design diagram · made in Skemio

System architecture showing News CMS publishing to a Fan-out Engine, writing to Kafka partitions, then consumed by APNs and FCM worker fleets connected to mobile devices.
System architecture showing News CMS publishing to a Fan-out Engine, writing to Kafka partitions, then consumed by APNs and FCM worker fleets connected to mobile devices.
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What it shows

  • Partition user device tokens into 10k chunks across distributed Kafka topics.
  • Maintain pre-warmed HTTP/2 persistent connection pools to Apple and Google APNs.
  • Track delivery and failure tokens asynchronously to keep worker throughput high.

The takeaway

Fan-out speed depends on token chunking, pipelining, and pre-warmed HTTP/2 pools.

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