83 shared libraries. Dozens of apps depending on them. Here's why a change to one doesn't take down the others.

83 shared libraries. Dozens of apps depending on them. The obvious question: how does a change to one not take down the others?

The answer is layering, enforced on purpose.

The libraries split into three tiers. A platform-agnostic core holds business logic that knows nothing about the browser or the phone. A web layer wraps it for Next.js. A native layer wraps it for React Native. An app never reaches past its layer into someone else's.

That boundary is what keeps a shared change safe. Fixing money math in the core can't accidentally import a browser API, because the core can't see the browser. The compiler enforces the architecture, instead of a code-review comment hoping someone remembers.

Most shared-code initiatives die because the shared layer becomes a junk drawer that couples everything to everything. The real discipline is drawing lines the tooling won't let you cross. Sharing more code is the easy part.

I've been maintaining this across a real, multi-app product suite, not a slide deck. It's the reason I can onboard a new app in days instead of weeks.

Want the exact core/web/native split I use? Comment and I'll lay it out.