When do you call another service with REST, and when do you publish a Kafka event?
PICTURE THIS: ASYNC / PROMISE
Simple meaning
Use synchronous REST when the user is waiting and you need an immediate consistent answer, like checking wallet balance.
WHY — Microservices instead of guessing?
Why interviewers care about Microservices:
on Microservices.
the situation, the default choice, and one exception - that reads as experience.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Use synchronous REST when
the user is waiting and you need an immediate consistent answer, like checking wallet balance.
- 2Publish an event when
other teams should react asynchronously, like sending email after order placed.
- 3How it works
Mixing both is normal
- 4do not block a
checkout on a marketing service.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Use synchronous REST when the user is waiting and you need an immediate consistent answer, like checking wallet balance. Publish an event when other teams should react asynchronously, like sending email after order placed.