Designing a Caching Layer for Tiny Objects

This chapter is inspired by Kangaroo: Caching Billions of Tiny Objects on Flash.

Tiny objects

Tiny objects are small information with a size that is ~100 bytes (B) or less. This information is crucial, unavoidable, and common. Tiny objects are prevalent in many large-scale systems:

• At Facebook, small objects are prevalent in the social graph. For example, the average social-graph edge size is under 100 B.

• At Twitter, tweets are limited to 280 B, and the average tweet is less than 33 characters. Due to the massive and growing number of tweets, Twitter seeks a cost-effective caching solution.

• At Microsoft Azure, a growing use case is processing updates from sensor data, such as IoT devices in Azure Streaming Analytics. For efficiency and availability, it caches the most popular metadata.