System Design: A Blob Store

This chapter designs storage for large, independently addressed objects. Start with the object interface, then consider how replication, access tiers, and deletion policies affect the cost of keeping those bytes.

What is a blob store?

A blob store is a storage solution for unstructured data, such as photos, audio, video, and binaries.

A blob is an object addressed by a name or ID and accompanied by metadata. This design uses a flat namespace within each container; name prefixes can resemble folders without creating directory objects. Although the examples emphasize unstructured media, a blob can also contain serialized structured data. The storage API treats its contents as bytes.

Write-once, read-many (WORM) retention is a specific protection policy, not an inherent property of every blob. Azure Blob Storage, for example, supports configured immutability policies that prevent changes or deletion during a retention period.