Choosing an event-driven architecture (EDA) for the backend of an application can significantly impact its scalability, maintainability, and overall success. Courier, a company that helps customers quickly design notifications and deliver them through their send endpoint, chose EDA backed by AWS as its backend architecture to ensure it could scale with various vectors such as quality, maintainability, ease of adding new features, and variable vs fixed infrastructure costs. By designing software around events, EDA promotes a highly decoupled system environment, allowing for independent work on code that reacts to events. This choice has brought numerous benefits, including focused functions, easy addition of observers, and monitoring capabilities with DataDog. However, it also presents challenges such as increased complexity in documentation and diagramming, difficulties in introducing changes to the event without affecting other handlers, and constraints when designing functions within the AWS stack. Despite these struggles, Courier believes its choice of EDA outweighs the cons, and it has matched its business needs for both short-term and long-term growth.