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Backend & LedgersProductionTimeline: 2024Role: Lead Backend Engineer

Shelter API — Faith-Based Mental Health Backend Platform

High-availability REST backend with Redis caching, JWT token rotation, and PostgreSQL transactions for therapy matching and resource delivery.

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The Problem

Healthcare applications require exceptionally strict privacy boundaries, low-latency resource serving, and continuous uptime without session hijacking risks.

The Architectural Solution

Designed a modular Node.js/Express TypeScript backend with Supabase PostgreSQL and Redis 7 cache. Implemented dual-token JWT authentication with sliding refresh tokens, revocation blacklists, and database connection pooling.

System Architecture & Flow

CANONICAL TOPOLOGY
[Client Application]
      │
      ▼
[Node.js 20 / Express TypeScript API]
      ├── JWT Auth Guard: Dual Access/Refresh token rotation
      ├── Redis 7: Endpoint response caching & token blacklist
      └── Modular Service Layer: Patient profiles, booking, content
      │
      ▼
[PostgreSQL 16 (Supabase Transaction Pooler)]

Engineering Contributions & Deliverables

  • Implemented secure dual-token authentication (short-lived access + sliding refresh) with automatic revocation in Redis.
  • Designed PostgreSQL schemas with foreign-key referential integrity and transaction isolation.
  • Reduced average endpoint response latency from 180ms to 24ms for cached resources via Redis 7.

Formal Security Invariants Enforced

AUDITOR VERIFIED
[1]Token Revocation Invariant: Logged-out or compromised refresh tokens are immediately blocked in Redis.
[2]Patient Data Privacy: No diagnostic or counselling note is queryable without explicit appointment-level authorization.

System Metrics

RuntimeNode.js 20
Cache Speedup7.5x Latency Reduction
Auth StandardJWT + Redis Rotation

Technology Breakdown

Core Runtime & Language
Node.js 20Express.jsTypeScript 5
Backend & Protocols
JWT RotationREST APIOpenAPI / Swagger
Databases & Ledgers
PostgreSQL 16Redis 7Supabase

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