Question 1

What is the difference between REST APIs and Event-Driven architecture?

Accepted Answer

REST APIs are synchronous; Service A asks Service B for data and waits (blocking) until B replies. In EDA, Service A fires an 'Event' into a queue and moves on immediately. Service B consumes that event whenever it's ready. This decoupling makes the overall system much faster and more resilient.

Question 2

When should I move to an Event-Driven architecture?

Accepted Answer

You should consider EDA when you have high-volume transactions, need real-time data streaming (like live dashboards or fraud detection), or when your microservices are suffering from tightly coupled dependencies that make scaling difficult.

Question 3

What does it cost to adopt an event-driven architecture?

Accepted Answer

EDA adds infrastructure like a message broker and more observability tooling, so it carries higher upfront cost than a simple synchronous app. The investment pays off when you have many services or high throughput; for a small CRUD app it is usually overkill, which we will tell you honestly during scoping.

Question 4

Which message broker should we use, Kafka, RabbitMQ, or a cloud service?

Accepted Answer

Kafka excels at high-volume event streaming and replayable logs, while RabbitMQ is simpler for task queues and routing. Managed options like AWS SNS/SQS or Google Pub/Sub reduce operational burden. We choose based on your throughput, ordering needs, and whether your team wants to run infrastructure.

Question 5

How do you prevent lost or duplicated events?

Accepted Answer

We design consumers to be idempotent so reprocessing the same event causes no harm, and use patterns like the transactional outbox to guarantee an event is published exactly when its database change commits. Dead-letter queues capture failures for safe retry instead of silent data loss.

Question 6

Can event-driven architecture integrate with our existing systems?

Accepted Answer

Yes. We commonly place an event layer alongside legacy systems using change-data-capture or adapter services, so old applications keep working while new ones subscribe to their events. This lets you modernize incrementally rather than replacing everything at once.

Question 7

How do you debug problems in an asynchronous system?

Accepted Answer

Because requests no longer follow a single thread, we add distributed tracing with tools like OpenTelemetry and correlation IDs that follow an event across services. This observability is non-negotiable in EDA, so we build it in from day one rather than bolting it on after an incident.

Question 8

Does going event-driven mean rewriting our whole application?

Accepted Answer

No. The most successful adoptions are incremental, introducing events for one bottleneck such as notifications or order processing while the rest stays synchronous. This lets you prove the value and build team expertise before expanding the pattern across the system.

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