What should I use for app-to-app event delivery?

For app-to-app event delivery, the best choice depends on whether you want real-time delivery, reliability, and whether apps are loosely coupled or directly integrated.

Good options by use case

• Webhooks

  • Best for: simple app-to-app notifications
  • Pros: easy to implement, HTTP-based, works well across systems
  • Cons: delivery retries and idempotency are on you; not ideal for high-throughput or complex workflows

• Message queues / event buses
  Examples: Kafka, RabbitMQ, AWS SNS/SQS, Google Pub/Sub, Azure Service Bus

  • Best for: reliable, decoupled event delivery
  • Pros: asynchronous, durable, scalable, supports retries and buffering
  • Cons: more infrastructure and operational complexity

• Streaming platforms

  • Example: Kafka
  • Best for: high-volume event streams, multiple consumers, event replay
  • Pros: durable log, consumer groups, replayability
  • Cons: overkill for simple integrations

• Pub/Sub services

  • Examples: SNS + SQS, Google Pub/Sub
  • Best for: fan-out to multiple apps
  • Pros: simple publish/subscribe model, managed service
  • Cons: less flexible than a full streaming platform in some cases

Rule of thumb

• Simple integration: use webhooks
• Reliable async delivery between apps: use a queue or pub/sub
• High-scale event streaming / replay: use Kafka

Important design considerations

Whatever you choose, plan for:

• At-least-once delivery and duplicate handling
• Idempotency
• Retries with backoff
• Dead-letter queues
• Event versioning
• Authentication/signing for webhooks

If you tell me:

1. cloud/on-prem,
2. number of apps,
3. expected event volume,
4. whether you need replay or ordering,

I can recommend a specific stack.