Problem Statement SaaS applications need real-time notification systems, but building one correctly is deceptively complex. Polling is unreliable, SSE is one-directional, and most teams bolt on a third-party widget rather than engineering the connection lifecycle, auth, preferences, and delivery guarantees properly from scratch.

Solution & Approach Built a production-grade WebSocket notification system using Socket.io with per-user rooms authenticated at the handshake level via JWT. The backend is a Node.js + Express + Prisma monorepo connected to NeonDB (serverless Postgres). Notifications are grouped by date, filterable by type (Mentions, Comments, Team Activity, System Alerts, Assignments), and preferences are persisted per-user per-category. A built-in simulator fires live demo events so reviewers can experience real-time delivery without any setup. Deployed on Google Cloud Run (backend) and Vercel (frontend).

Key Highlights WebSocket rooms authenticated at handshake via JWT — no unauthenticated connections possible 7-filter notification center: All, Unread, Mention, Comment, Team, System, Assignment Per-user per-category preferences with live inApp and email toggles Built-in notification simulator for live demo without reviewer setup Auto-reconnect with exponential backoff on network drop