Building Real-Time Messaging in a Next.js SaaS with Server-Sent Events

A Next.js property management SaaS used Server-Sent Events instead of WebSockets for real-time landlord-tenant message updates.

Messages are stored in MongoDB via Prisma, posted through a POST endpoint, and streamed to clients over an EventSource connection.

Auth, role checks, and Zod validation run before events are delivered, helping keep the message flow secure and reliable.

The example shows SSE can be a lightweight fit for apps that only need server-to-client updates.

Its tradeoffs are that SSE is one-way and long-lived connections can be hard to maintain in serverless hosting like Vercel.