# How Apple built iCloud to store billions of databases

DevFeed: [How Apple built iCloud to store billions of databases](<https://devfeed.tech/articles/how-apple-built-icloud-to-store-billions-of-databases-39087.md>)

Original publisher: [Read original article](<https://read.engineerscodex.com/p/how-apple-built-icloud-to-store-billions>)

Author: Engineer's Codex

Published: 2024-01-14T21:53:05Z

Content type: article

Language: en

Sources: [Engineer's Codex](<https://devfeed.tech/sources/engineer-s-codex.md>)

Topics: [Apache Cassandra](<https://devfeed.tech/topics/cassandra.md>), [Database](<https://devfeed.tech/topics/database.md>), [Multitenancy](<https://devfeed.tech/topics/multitenancy.md>), [Cloud](<https://devfeed.tech/topics/cloud.md>), [NoSQL](<https://devfeed.tech/topics/nosql.md>), [Architecture & Design](<https://devfeed.tech/topics/architecture-design.md>), [Scalability](<https://devfeed.tech/topics/scalability.md>)

Tags: [architecture](<https://devfeed.tech/tags/architecture.md>), [cassandra](<https://devfeed.tech/tags/cassandra.md>), [cloud](<https://devfeed.tech/tags/cloud.md>), [database](<https://devfeed.tech/tags/database.md>), [nosql](<https://devfeed.tech/tags/nosql.md>), [scalability](<https://devfeed.tech/tags/scalability.md>), [separate](<https://devfeed.tech/tags/separate.md>)

## AI overview

This article examines how Apple built iCloud and CloudKit using FoundationDB and Cassandra. It discusses the systems' extreme multi-tenant architecture and engineering choices such as asynchronous processing, stateless design, resource isolation, and layered abstractions to support scalability, reliability, availability, and developer experience.

## Source excerpt

Apple uses Cassandra and FoundationDB for CloudKit, their cloud backend service. We take a look into how exactly each is used within their cloud and the problems they've solved.