What should I use for real-time app-to-app events?

For real-time app-to-app events, the best choice usually depends on whether you want instant delivery, reliability, or simple integration.

Common options

1. WebSockets

• Best for live, bidirectional communication
• Good for chat, collaboration, dashboards, games
• Keeps a persistent connection open
• More work to scale and manage connections

2. Server-Sent Events (SSE)

• Good for one-way updates from server to client
• Simpler than WebSockets
• Great for feeds, notifications, progress updates
• Not ideal if the client needs to send frequent messages back

3. Message queues / event buses

Examples: Kafka, RabbitMQ, NATS, Redis Streams

• Best for app-to-app backend events
• Reliable, decoupled, scalable
• Good when services need to react to events asynchronously
• Not directly for browser real-time UI, but often paired with WebSockets/SSE

4. Pub/Sub platforms

Examples: Firebase, Pusher, Ably, PubNub

• Fastest way to add real-time features
• Handles scaling, reconnects, fan-out
• Good for teams that want less infrastructure

Quick recommendation

• Browser/client real-time UI: WebSockets or SSE
• Backend-to-backend events: Kafka, NATS, RabbitMQ, or Redis Streams
• Fastest managed solution: Pusher / Ably / Firebase

Rule of thumb

• Use WebSockets if you need two-way real-time interaction
• Use SSE if you only need server → client updates
• Use Kafka/NATS/RabbitMQ if you mean internal app-to-app event streaming

If you tell me whether this is mobile app, web app, or service-to-service, I can suggest the best fit.