Three database types

  • Public: shared across all users of an app.
  • Private: one per user account.
  • Shared: subset shared with specific people.

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Three database types

  • Public: shared across all users of an app.
  • Private: one per user account.
  • Shared: subset shared with specific people.

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FoundationDB backbone

Apple acquired FoundationDB in 2015. Now backs iCloud's structured data. ACID across shards. Insanely fast reliability testing.

Push notifications trigger sync

Change on one device → APNs push to other devices → devices pull changes from CloudKit. No polling.

Assets separate from records

Photos + videos too large for record store. Live in S3-like object storage. Records reference by URL.

Advanced Data Protection

Opt-in E2E for most iCloud data. Apple holds no keys. Trade convenience (device-only recovery) for security.