Welcome back to The Everyday Backend Engineer: Practical Design Patterns. In our last post, we made our core algorithms interchangeable using the Strategy Pattern. Today, we close out our design patterns roadmap with arguably the most native pattern in the entire Node.js ecosystem: The Observer Pattern.
Let’s look at how to master event-driven decoupling to trigger secondary workflows seamlessly without bloat.
Imagine you are writing a video processing engine or a simple order fulfillment system. When a specific event happens—such as an order being finalized—multiple unrelated departments want a piece of the action:
The Notification Service needs to send an SMS and Email receipt.
The Logistics Service needs to generate a warehouse fulfillment ticket.
