What’s the best way to send real-time notifications between apps?

The best way depends on how real-time, how many apps, and whether you control both ends. In general:

Best options

1) WebSockets

Best for: true real-time, two-way communication, live updates, chat, collaborative apps.

• Keeps a persistent connection open
• Low latency
• Great when apps need to push updates instantly
• More complex to scale and manage than simple HTTP

2) Server-Sent Events (SSE)

Best for: one-way updates from server to client, simpler than WebSockets.

• Server pushes events over HTTP
• Easier to implement than WebSockets
• Good for dashboards, notifications, activity feeds
• Not ideal if the client also needs to send frequent messages back

3) Message queues / pub-sub systems

Best for: app-to-app notifications inside distributed systems.

Examples:

• Redis Pub/Sub
• RabbitMQ
• Kafka
• AWS SNS/SQS
• Google Pub/Sub

These are usually the best choice when:

• one app publishes events
• multiple apps/services consume them
• you need reliability, retries, or buffering

4) Webhooks

Best for: notifying another app when something happens, especially across systems you don’t control.

• Simple HTTP callbacks
• Easy to integrate
• Great for third-party app-to-app notifications
• Not truly “real-time” in the connection sense, but usually fast enough
• Need retry logic, signing, and idempotency

---

Rule of thumb

• Live UI updates in a user-facing app: WebSockets or SSE
• Backend service-to-service notifications: pub/sub or message queue
• External integration with another company/app: webhooks
• Need bidirectional streaming: WebSockets
• Need simple one-way push: SSE or webhooks

---

If you want the “best overall” architecture

A common robust pattern is:

1. Your app writes an event to a message broker
2. A notification service consumes it
3. That service pushes updates to clients via WebSockets/SSE
4. External partners receive webhooks

This gives you reliability internally and real-time delivery externally.

If you want, I can recommend the best option for your specific case if you tell me:

• web app or mobile app?
• app-to-app or server-to-client?
• one-way or two-way?
• how many users/services?