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Open WhatsApp →Open Instagram Feed →

WhatsApp vs Instagram Feed

WhatsApp

WhatsApp

Persistent connections, message queues, delivery.

Components (8)

  • Sender
  • WS Gateway
  • Chat Service
  • Presence
  • Cassandra
  • Kafka
  • APNs / FCM
  • Recipient

Headline numbers

  • Messages / sec (avg)~1.2M/sec
  • Cassandra writes / sec~2.4M/sec
  • Storage / day~12 TB
Instagram Feed

Instagram Feed

Fan-out on write vs read, ranking, CDN.

Components (10)

  • Mobile Client
  • CDN
  • API Gateway
  • Feed Service
  • Post Service
  • Kafka
  • Fan-out Worker
  • Redis
  • Postgres
  • S3

Headline numbers

  • Posts / sec (avg)~3,000/sec
  • Feed read QPS~58,000/sec
  • Fan-out writes / sec~600,000/sec

Key differences

Only in WhatsApp
  • APNs / FCM
In both
  • Client
  • Api Gateway
  • Service
  • Cache
  • Database
  • Queue
Only in Instagram Feed
  • CDN
  • S3

Flow shape

WhatsApp flows
  • Send message (recipient online)6 steps
  • Send message (recipient offline)7 steps
  • ⚠ APNs / FCM is down7 steps
  • ⚠ WS Gateway box dies3 steps
Instagram Feed flows
  • Post a photo (fan-out on write)7 steps
  • Open feed (precomputed timeline)5 steps
  • ⚠ Fan-out Worker is down7 steps
  • ⚠ Timeline cache flushed (Redis restart)4 steps