Amazon EventBridge
Managed event bus with content-based routing, how it differs from SNS, and connecting it directly to API Gateway without a transport Lambda.
A managed, serverless event bus. Producers publish events onto a custom bus, and any number of subscribers can receive them, a publish-subscribe system with scaling built in.
vs SNS
Both are managed pub-sub services on AWS. The difference is how each decides where an event goes.
- SNS routes by topic. A publisher sends to a topic, every subscriber to that topic gets the message.
- EventBridge routes by content. An event rule inspects the whole event, body, headers, metadata, and decides the target based on what's actually inside it.
Content-based routing is the reason to reach for EventBridge over SNS: if type equals X, route to Y.
Direct service integrations
API Gateway can publish straight to EventBridge without a Lambda function in between. Skip the Lambda unless it needs to transform the payload, not just move it, a transport-only Lambda adds execution cost and cold-start latency for zero benefit.
Extensibility
A new event rule has a blast radius of exactly the new feature it's for. It doesn't touch the routes, functions, or queues an existing feature depends on, which is the opposite of adding a new if/else branch to a shared function.
Where this showed up
- A Lambda that only moves data is a Lambda you don't need: direct API Gateway integration, EventBridge vs SNS.
- A new rule, not a rewrite: extensibility stress test.