A global eSIM app with VoIP calling, built and shipped alone.
Twenty-six months as the only engineer: the Flutter app, the Next.js admin dashboard, and both store submissions.
The product
Travellers buy an eSIM data plan for a country or region, install it in-app, and call over VoIP without a local SIM. DennisMobile B.V. is based in the Netherlands; users are anywhere.
What I built
The Flutter app for iOS and Android: plan catalogue, checkout, eSIM install flow, VoIP dialer and call history, usage tracking. The Next.js admin dashboard for plans, customers and support. Both store listings, from the first submission to the last update.
What was hard
eSIM installation differs by OS version and carrier, and cannot be tested on a simulator. VoIP audio routing on Android took several rewrites. Being the only engineer meant every store rejection was mine to resolve, on my own clock, eight hours ahead of the client.