Real-Time Systems

Persistent connections, presence, pub/sub fanout, geo-indexed dispatch: designs where seconds matter.

1. 1
   Chat (Slack-style)Intermediate

   Room-based pub/sub fanout across gateway instances.
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2. 2
   WhatsAppAdvanced

   Persistent connections, message queues, delivery.
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3. 3
   Uber (Driver Matching)Advanced

   Geo-indexing, dispatch, real-time location streams.
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