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Digital productsSeptember 2023–March 2024Contract work

Fixing existing apps and adding face and fingerprint sign-in

I led improvements to several existing apps without a full rewrite. They shared one code repository and a server layer tailored to the apps, on a platform serving multiple customer organisations. I also added face and fingerprint sign-in.

UIC Digital · official job title: Lead Fullstack React Native Development Expert

The situation

Several existing apps needed their structure put in order.

What made it hard?

At the same time, we had to add face and fingerprint sign-in without rewriting the apps from scratch.

What was I responsible for?

  • I reviewed how the apps were built and made the way they fetch data from the server consistent (TanStack Query).
  • I built the system on one shared code repository (a monorepo), with a separate NestJS server layer for the apps (a BFF). The platform served multiple customer organisations in isolation.
  • I wrote Swift and Kotlin modules so the apps use the phone's own face recognition and fingerprint reader for signing in.

Decisions and reasons

I sorted out data fetching first
That way the new sign-in fetches data the same way as the rest of the app, with no special cases.

Results

  • Roughly 40% less repetitive boilerplate code.
  • The share of successful, secure sign-ins improved by 15%.
  • The apps loaded in 0.3 seconds instead of 10.

When this matters to you

  • If an existing app needs fixing and extending, a rewrite is not the first thing I will suggest.