Top 3 Event driven Interview Questions

Browse 3 real-world technical and behavioral interview questions about Event driven. Review scenarios, edge cases, and architectural best practices.

Your services talk through events and one consumer has been down for an hour. What has it missed, and how does it catch up?

A Kafka-style consumer down for an hour has missed an offset range, not necessarily lost data. If retention still covers the gap, it resumes from the committed offset; catch-up needs surplus throughput, idempotent handlers, event-time logic and a plan for retention expiry. Use this event driven answer to show the decision, trade-off, and evidence rather than a memorised definition.

hardscenario

You need to add one field to an event and remove another, and five teams consume it. How does that roll out?

Additive changes with defaults are safe, removals are not, so split every removal into deprecate-then-delete with evidence that nobody reads the field. Register the schema, pick a compatibility mode deliberately, and note that backward compatibility requires consumers to deploy first.

harddesign

Service A needs something from service B. When should that be a synchronous call and when should it be an event?

A synchronous call couples availability and latency but keeps the outcome knowable at the point of decision; an event decouples both but converts every failure into something the caller will never learn about. Choose by asking whether the caller needs the answer to proceed, not by which style is fashionable.

mediumdesign