Your Monorepo Builds Take 20 Minutes Because Yarn Workspaces Is Broken

Last Thursday at 2:30 PM, middle of a hotfix deploy, Yarn Workspaces decided that our authentication package couldn't find bcrypt anymore. Same code that had been working for 6 months. Same lockfile. Same everything. The error:

Module not found: Can't resolve 'bcrypt' in '/packages/auth/src'

But here's the thing - bcrypt was right there in our package.json dependencies. VSCode saw it. TypeScript was happy. Even `yarn why bcrypt` showed it installed correctly. But the webpack build? Nope. "Never heard of bcrypt, must be imaginary."

Spent 3 hours figuring out that hoisting had moved bcrypt into some nested path because we updated a totally unrelated UI package. Yarn's hoisting algorithm saw that update and thought "you know what? Let's reorganize EVERYTHING." No warning. No explanation. Just suddenly our production auth was broken.

The "Phantom Dependency" Game

This is the thing that makes Yarn Workspaces actually dangerous. Your code imports something, your editor confirms it exists, your build passes locally. Then production deploys and everything breaks because hoisting is completely unpredictable.

Package A used to import lodash from the root. Package B gets updated with a newer lodash version. Suddenly Package A's import breaks because Yarn decided the root lodash needed to move. The best part? This only happens sometimes. Like maybe 40% of deployments. The other 60% it works fine, so you never know if you're about to break production.

Our deploy checklist now includes "pray to whatever gods handle dependency resolution" right after the security scan.

The npm hoisting behavior is documented but the Yarn implementation has subtle differences that can break builds. Even Node.js module resolution doesn't guarantee where packages end up.

What Actually Works

PNPM Workspaces solved the phantom dependency problem in about 2 hours. It creates proper isolated node_modules for each package instead of relying on hoisting magic. If a package imports something, it better damn well declare it as a dependency.

Turborepo cut our build times from 18 minutes to 4 minutes with zero configuration. Just works. Cache hits, builds skip. Revolutionary concept.

Nx is the nuclear option. Learning curve from hell but once you get it, builds that used to take 20+ minutes finish in under 2 minutes. Their dependency graph analysis actually knows what changed.

The breaking point for switching isn't subjective - it's when your deploy process includes crossing your fingers that hoisting doesn't break production. That's not engineering, that's gambling.

I've been debugging the same Turborepo caching issue for 3 weeks now. It's driving me insane. The cache says nothing changed, serves me stale builds, and my API endpoints throw runtime errors because they're using old TypeScript interfaces.

Here's what happens: I change a function signature in our shared utils package. TypeScript compiles fine. Tests pass locally. Turborepo says "cache hit!" and deploys the old version of dependent packages. Production APIs start throwing Property 'newField' does not exist errors because half the services got the new interface and half got cached old builds.

The cache invalidation logic is a fucking black box. Change one tiny thing? Full rebuild. Change something that actually breaks downstream packages? "Cache is fresh, bro!"

The Command That Never Works

`turbo prune` is supposed to fix cache issues. It doesn't. Here's what I've tried:

turbo prune           # "Pruned 0 items"
turbo prune --force   # Still serves stale cache
rm -rf .turbo/cache   # Nuclear option, still cached somewhere

The cache lives in like 5 different places. Local .turbo/cache, some global cache directory, Vercel's remote cache, and probably your browser's local storage at this point. Clearing one doesn't clear the others.

When Cache Hits Are Actually Cache Lies

Last Tuesday I spent 4 hours debugging why our checkout flow was broken in staging. Turned out Turborepo cached a build from 2 days ago when I accidentally reverted a payment processing change. The cache fingerprint somehow matched even though the code was completely different.

The hash algorithm apparently thinks these are identical:

• Code that processes credit cards correctly
• Code that was broken 2 days ago

But it rebuilds everything when you change a comment in a README file.

The Turborepo team knows about this but their suggested cache debugging steps don't help when the cache is confidently wrong.

The --force Flag Is Your Only Friend

I've started running `turbo build --force` for anything that touches shared interfaces. Defeats the entire purpose of caching but at least my builds work.

Team lead asked why our "fast build tool" takes 15 minutes now. Had to explain that fast builds don't matter if they deploy broken code.

What Actually Works Consistently

PNPM doesn't have caching so it can't lie to you. Builds take longer but they're correct every time. No cache invalidation bugs because there's no cache to invalidate.

Nx has better dependency tracking. When I change a shared interface, it correctly identifies the 12 packages that depend on it and rebuilds all of them. Takes some time to set up but the dependency graph actually works.

The breaking point isn't build speed - it's trust. Can't use a tool that randomly serves stale builds and calls them fresh. Would rather wait 10 minutes for a correct build than get a 30-second build that breaks production.