Design Object Storage (like S3)
Last Updated: December 29, 2025
Object storage is a data storage architecture that manages data as discrete units called objects, rather than as files in a hierarchy or blocks on a disk. Each object contains the data itself, metadata describing the object, and a unique identifier.
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Unlike traditional file systems that organize data in directories and subdirectories, object storage uses a flat namespace where every object is accessed via its unique key. This architecture enables massive scalability, as the system can store billions of objects without the limitations of hierarchical file systems.
Popular Examples: Amazon S3, Google Cloud Storage, Azure Blob Storage, MinIO
This system design problem touches on so many fundamental concepts: distributed storage, data durability, consistency models, replication strategies, and large-scale data management.
The challenge is not just storing bytes, it is storing them reliably across hardware that will inevitably fail, at a scale that spans petabytes, while serving thousands of requests per second.
In this article, we will explore the high-level design of an object storage system like Amazon S3.
Let's start by clarifying the requirements: