Platform Events
By the end of this lesson, you'll be able to:
- Explain what a platform event is and the publish/subscribe pattern it enables
- Publish a platform event from Apex
- Recognize when platform events fit better than a direct callout
Prerequisites: "SOAP Web Services Overview"
Publish/subscribe: a different integration shape
Every earlier lesson in this module was a direct, point-to-point connection: Apex calls one specific external system, or one external system calls one specific Apex endpoint. A platform event is different — Apex publishes a message, and any number of subscribers (other Apex triggers, external systems via a streaming API, automation tools) can react to it independently, without the publisher knowing or caring who's listening.
Publishing a platform event
Order_Shipped__e event = new Order_Shipped__e(
Order_Id__c = '801XX0000000001',
Tracking_Number__c = 'TRK-9876'
);
Database.SaveResult result = EventBus.publish(event);
if (result.isSuccess()) {
System.debug('Event published successfully.');
}Order_Shipped__e — note the __e suffix, this platform's version of the __c/__mdt suffixes seen throughout this course — is a custom platform event definition, published via EventBus.publish() rather than a regular insert DML statement.
When this fits better than a direct callout
If three different systems all need to know "an order shipped" — a shipping-notification email, an external accounting system, and an internal analytics dashboard — a direct callout approach would need Apex code that explicitly calls all three, one by one, and grows more complicated every time a fourth subscriber is added. Publishing one platform event lets each subscriber react independently, with the publisher never needing to change as subscribers are added or removed — a genuinely more decoupled integration shape.
Exercise
As a comment, explain why a platform event is a better fit than three separate direct callouts for the "three systems need to know an order shipped" scenario.
Show hint
Think about what happens when a fourth subscriber needs to be added later.
Platform Events Quiz
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Summary
A platform event is a message Apex can publish that any number of subscribers — inside or outside Salesforce — can react to, without the publisher needing to know who's listening.