Real-Time Systems & Cryptography

Sentinel – Offline-First Security Platform

Role: Lead System Architect   //   Timeline: 2025 – 2026

Sentinel – Offline-First Security Platform architecture

Core Metrics

  • Processed 470+ live attendees concurrently with zero downtime
  • Maintained accurate chronology for offline scans by syncing in optimal batches of 20

Technology Stack

Languages

TypeScript

Orchestration

Supabase Realtime, Next.js

Data Layer

PostgreSQL, Prisma ORM

Frontend

React Native, Expo, Tailwind CSS

The Problem & Constraint

An enterprise-grade access-control platform that processed hundreds of live event attendees with zero downtime, solving high-density venue cellular latency through offline cryptographic verification.

System Topology

Mobile scanners (React Native) bypass venue network latency by utilizing an offline-first architecture, generating TOTP tokens locally. Backend state is synchronized optimistically. The admin dashboard leverages Supabase Realtime (Postgres Change Data Capture) to compute live venue occupancy instantly.

Engineering Tradeoffs

  • 01

    Implemented a Time-based One-Time Password (TOTP) QR engine using SHA-1 hashing, 20-byte Base32 secrets, and a ±60-second time-drift window.

  • 02

    Built strict anti-passback transaction guards using Prisma `$transaction` isolation levels to atomically reject duplicate entry states and prevent replay attacks.