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Usapp

End-to-end encrypted messaging on iOS and Android, and the push-notification backbone for every other company product.

  • backend
  • mobile
  • DevSecOps

▲ Live on iOS and Android · adopted as the push-notification backbone for every other company product.

demo ↗
Usapp cover
/work/usapp/cover.webp · 16:10

problem

Users needed private messaging where the server itself cannot read message content.

my role

Sole developer & architect: mobile client, distributed backend microservices, deployment pipeline, and production server operations, all built and run single-handedly.

key decisions

  1. End-to-end encryption with client-side keys, so the server never sees message content.
  2. Passwordless OTP sign-in with revocable device sessions.
  3. WebSocket delivery coordinated through Redis across gateway instances.
  4. A partner API for outside organizations.
  5. Full CI/CD pipeline with automated security scanning and signed artifacts.

stack

  • React Native (Expo)
  • NestJS
  • gRPC
  • RabbitMQ
  • Socket.IO
  • Redis
  • PostgreSQL
  • MongoDB

evidence

Usapp

live systems

A live conversation: end-to-end encrypted, with delivery and seen receipts. Built solo across the mobile client, the microservices behind it, and the servers it runs on.

captured 2026-09-08 · usapp.ph

usapp.ph ↗

screens

System architecture
/work/usapp/architecture.webp · 16:10
System architecture
Main screen
/work/usapp/screen-1.webp · 9:19.5
Main screen
Key workflow
/work/usapp/screen-2.webp · 9:19.5
Key workflow
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