Request coalescing: 2 real scaling case studies
2 of the 94 engineering write-ups in our database are tagged with the technique "request coalescing". They come from 2 companies (Cloudflare and Discord) and were published between 2023 and 2026. 2 of the 2 state concrete scale numbers, for example "R2 p99 time to first byte roughly halved (hits and misses)" (Cloudflare). Each card below links to our short summary and the original post.
Origin Range Requests: Serving large files without range-request tuning
Cloudflare's old range-request caching sliced files into a per-zone configured range size, so a small video seek could pull 128 MiB from origin for R2, while small ranges caused floods of tiny origin requests and memory pressure, and concurrent requests in the same range blocked each other. Moving from nginx to its Pingora-based cache, it reused Pingora's fixed-size on-disk chunks as the unit: a coordinator serves cached bytes, attaches to in-flight downloads, fetches only missing chunk-aligned ranges from origin, and validates size and ETag before composing one 206 response. For R2, p99 time to first byte dropped by about half, and letting one response combine disk and upstream bytes cut tiered cache traffic about 6% week over week.
How Discord Stores Trillions of Messages
Discord moved its message store from Cassandra to ScyllaDB and put Rust data services in front of it to coalesce hot-partition requests.