DEV Community

Cover image for Cache transfers wait on the network
VX
VX

Posted on Edited on Originally published at vznjs.github.io

Cache transfers wait on the network

#javascript #monorepo #devtools #opensource

Cache uploads and downloads mostly wait on the network, so vx runs up
to 64 at once even on a 4-core machine. 1,000 uploads to a cache 30 ms
away take 2.5 s. With only 4 at once:

$ time vx run build --all --cache-concurrency-upload 4
  cache     remote 1000↑ 269 KB
  time      2.27s
real    0m8.345s

$ time vx run build --all
  cache     remote 1000↑ 269 KB
  time      2.38s
real    0m2.649s
Enter fullscreen mode Exit fullscreen mode

The run's time ends with its last task. Uploads finish in the
background, and the process exits when they are done.

Lane limit Upload all 1,000 Restore all 1,000 from the remote
1 31.6 s 9.0 s
4 8.4 s 8.4 s
16 2.7 s 2.6 s
default (64) 2.5 s 1.6 s

Min of 3 interleaved runs · private/vx-bench/generate.ts, 1,000 projects, build --all · Turborepo-protocol cache that answers after 30 ms, turboCache() · CI=1 · Linux x64, 4 cores · vx a1786b3 · 2026-10-23

Three lanes, three limits

Lane Default Why
download min(96, max(cores × 3, 64)) mostly waiting on the network
upload min(96, max(cores × 3, 64)), per remote the same, and it runs in the background
restore twice run.concurrency local disk work, closer to a task

The network formula is pnpm's: at least 64 at once, at most 96. If your
server wants fewer connections, set fewer:

// .vx/workspace.ts
import { defineWorkspace } from '@vzn/vx/config'

export default defineWorkspace({
  cache: { concurrency: { download: 32, upload: 16 } },
})
Enter fullscreen mode Exit fullscreen mode 
vx run build --all --cache-concurrency-upload 16
Enter fullscreen mode Exit fullscreen mode

A missing key costs no request

diagram

Before tasks start, vx asks each remote in one batch which keys exist.
A missing key costs nothing more. A key it has costs one download.

One request per plugin read

Plugins keep entries in the same cache, like the timings
@vzn/vx-schedule-history learns. ctx.cache.get, has and hasMany
each make one request.

Settings: schema. Flags: CLI reference.
More at vznjs.github.io/vx.

Originally published on the vx blog. vx is open-source (MIT) task orchestration with a build cache: vznjs.github.io/vx · GitHub.

Written with AI assistance.

Top comments (0)