Ubiquitous Caching: A Journey of Building Efficient Distributed and In-Process Caches at Twitter

Modern web applications widely deploy cache across the stack to speed up data access and improve throughput.

In this talk, I will discuss three trends in hardware, workload, and cache usage that shape the design of modern caches.
The slow down of memory capacity scaling, the exploding data creation rate, and the wide adoption of Time-to-live (TTL) motivated the design of Segcache (https://paper.segcache.com and https://open-source.segcache.com).

Segcache is a new cache storage design that provides high memory efficiency and high throughput via metadata sharing to save space wasted on metadata, approximate indexing to efficiently remove short-lived data, and macro management for high throughput and linear scalability.
The design of Segcache is driven by the insight that key-value cache is different from key-value store + eviction, and is the outcome of exploring different trade-offs between caching and storage.

We deploy Segcache as standalone distributed caches and embedded off-heap caches for JVM-based microservices at Twitter. The distributed cache deployment significantly reduces the resources (CPU/DRAM) provisioned for cache clusters; the embedded deployment allows us to speed up data access and reduce GC pause time.