When should you choose event‑driven architecture over request‑response, and how do you justify its use in terms of decoupling, scalability, and reliability?

Event‑driven architecture is the right choice when you need loose coupling between services, high throughput, and the ability to scale components independently. By publishing events to a broker, producers do not wait for consumers, which eliminates blocking and allows each service to process at its own pace. Decoupling also means that adding or removing a consumer does not affect the producer, improving maintainability. Scalability is achieved because you can spin up more consumers to handle increased load without touching the producer. Reliability comes from the broker’s persistence and retry mechanisms; if a consumer fails, the event can be retried or routed to a dead‑letter queue. In contrast, request‑response ties the caller to the callee; a failure in one service can cascade, and scaling is limited by the synchronous call chain. Therefore, for scenarios such as order processing, analytics pipelines, or IoT telemetry, event‑driven architecture provides the necessary decoupling, scalability, and resilience.