Ship the Feature as a Package, Not a Copy-Paste

The third time you build the same login screen, you should stop building login screens. Here's how treating onboarding as a product — an installable package — beat rebuilding it for every app.

The trap: bespoke every time

Each app reinvented auth slightly differently: OTP in one, password-first in another, social login bolted on inconsistently, branding hard-coded. New apps spent weeks rebuilding flows that already existed, and the small differences leaked into a fragmented user experience.

Reframe: configuration over code

The fix was to design onboarding as a configurable package any Node app can install:

• Pluggable methods — OTP, MPIN, password, Google/Facebook SSO — turned on and ordered via config, not code.
• Branding and copy controlled from an admin panel, so non-engineers tailor the experience per product without a deploy.
• A backend for configuration + auth workflows, with a cache layer so config reads stay fast.

The hard part isn't the auth — it's the boundaries

Building a reusable package is harder than building a one-off, and the difficulty is mostly API design:

• Constrain the configuration surface. Total flexibility becomes an untestable matrix of states. A well-defined config schema keeps the flexibility honest and the package testable.
• Version like a library author. Once a second app depends on you, every change is a compatibility decision. Semantic versioning and a changelog stop being optional.
• Make the defaults good. The fastest integration is one where the defaults are sensible and you only configure what's different.

Why it was worth it

The payoff compounds with every adopter. Across four Angular apps and 15–20 clients, a new app gets full auth and onboarding by installing the package, and operations can reconfigure onboarding journeys, branding, and login methods in 5–10 minutes instead of waiting for a release. Because every app shares the same configurable core, the onboarding experience finally felt consistent.

Build it once, configurably, and let the next team npm install instead of copy-paste.