Question 1

How do Nest microservices differ from HTTP controllers?

Accepted Answer

They use transporters (TCP/Redis/NATS/Kafka/RabbitMQ/gRPC) with @MessagePattern/@EventPattern handlers. Hybrid apps can listen to both HTTP and microservice channels. Serialization and idempotency matter more.

Question 2

Request-response vs event patterns in Nest microservices?

Accepted Answer

MessagePattern expects a response; EventPattern is fire-and-forget style consumption. Choose based on coupling needs. Events need consumer resilience and duplicate handling.

Question 3

Why is idempotency critical for Kafka/Rabbit consumers?

Accepted Answer

At-least-once delivery means duplicates — handlers must tolerate retries safely. Store processed keys, use upserts, and design side effects carefully.

Question 4

gRPC with Nest — when prefer it?

Accepted Answer

Internal service meshes needing typed contracts, streaming, and efficient binary protocols. Protobuf contracts become your API. Harder browser exposure — often behind gateways.

Question 5

Debugging: Nest microservice hangs waiting for response.

Accepted Answer

Client timeout, no handler, transporter misconfig, or server crashed mid-request. Add timeouts, health checks, and correlation IDs across the hop. Verify patterns match.

Question 6

Lead: when NOT to split a Nest monolith into microservices?

Accepted Answer

When the team/domain boundaries aren't clear, ops maturity is low, or the problem is modularity not scale. Start with modular monolith Nest modules. Split along failure domains and team ownership later.

Microservices NestJS Interview Questions

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