Describe how you handle event triggers and notifications to users.

In an event‑driven system, events are the primary means of communication between services. I start by defining the event schema and the event bus (e.g., Kafka, AWS EventBridge, or a simple message queue). When a business action occurs—such as a user signing up—I publish an event to the bus. Subscribers, which can be microservices or serverless functions, consume the event asynchronously. For user notifications, I typically use a dedicated notification service that listens to relevant events. When it receives an event, it formats a message (email, SMS, push notification) and sends it via an external provider (SendGrid, Twilio, Firebase). I also implement idempotency and retry logic to handle transient failures. Monitoring is crucial; I use metrics and alerts to track event delivery latency and failure rates. This decoupled approach allows the system to scale independently, ensures that the notification logic does not block the core business flow, and provides a clear audit trail of user interactions.