System Design
Messaging & Event-Driven
6 practice questions. Free questions open a full answer guide; the rest unlock with Pro.
- Design a notification system that sends order-status updates to users across email, SMS, and push. How do you keep it reliable and decoupled from the services that trigger notifications?
- Design a payment-processing endpoint that stays correct when clients retry requests after timeouts. How do you prevent double charges?Go Pro
- Design an event-sourcing architecture for a financial transactions system. Handle auditability, replay, and eventual projections.Go Pro
- Design a batch-to-streaming ETL migration for a pipeline that processes 500 GB of event data per day, currently running nightly.Go Pro
- Design a notification service that sends email, SMS, and push notifications to millions of users. Events are triggered by other microservices.Go Pro
- Design a notification fan-out system that sends transactional messages (email, SMS, push) triggered by domain events, and explain how you guarantee a user is never double-charged a notification — e.g. two 'payment received' emails — even though the network and your workers can fail and retry at any point.Go Pro
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