Question 1

Is Nest only for microservices? What default architecture fits most teams?

Accepted Answer

A modular monolith with clear Nest modules is often best until boundaries demand distribution. Nest's DI/modules shine in monoliths. Microservices add ops cost — earn them.

Question 2

Clean/hexagonal architecture mapping onto Nest?

Accepted Answer

Controllers as adapters; services as application/domain; ORM repos as infrastructure providers behind ports. Don't over-abstract early, but keep domain pure enough to test. Tokens for ports.

Question 3

Config management best practices in Nest?

Accepted Answer

ConfigModule/validation with Joi/Zod at boot, no raw process.env sprinkled, secrets from vault/env. Fail fast on missing config. Separate config per environment. Never commit secrets.

Question 4

Scenario: circular dependency between OrdersModule and UsersModule.

Accepted Answer

Extract shared kernel or interactions via events/application service in a higher module; avoid bidirectional imports. forwardRef is a bandage. Redesign ownership of the relationship.

Question 5

How do you approach background jobs in Nest apps?

Accepted Answer

Queues (Bull/BullMQ) with dedicated processors, retries, and separate scaling from HTTP pods. Keep job handlers idempotent. Observe lag. Don't run heavy jobs on web processes without isolation.

Question 6

Lead: evolve a Nest monolith toward service extraction.

Accepted Answer

Identify bounded contexts with separate DBs need, extract module to package to service, introduce anti-corruption layers. Strangler pattern via gateway. Measure independently scalable parts. Resist premature split of every module.

Architecture NestJS Interview Questions

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