NestJS NestJS Database Integration & ORMs 2

Question 1

How do you configure TypeORM for asynchronous configuration (e.g., from ConfigService) in NestJS?

Accepted Answer

TypeOrmModule.forRootAsync() with useFactory

Answer

TypeOrmModule.forRootAsync() accepts a useFactory (or useClass/useExisting) that can inject ConfigService and return the database options asynchronously.

Question 2

What does the `synchronize: true` TypeORM option do and why is it dangerous in production?

Accepted Answer

It automatically alters the DB schema to match entities — risking data loss on production

Answer

`synchronize: true` auto-runs ALTER TABLE statements on startup to match entity definitions, which can drop columns or tables with production data.

Question 3

Which Prisma CLI command generates the Prisma Client after schema changes?

Accepted Answer

prisma generate

Answer

`prisma generate` reads the schema.prisma file and generates the type-safe Prisma Client that your NestJS services use.

Question 4

How do you implement soft deletes in TypeORM within a NestJS application?

Accepted Answer

Use the @DeleteDateColumn() decorator and call repository.softDelete()

Answer

@DeleteDateColumn() adds a nullable timestamp column; repository.softDelete() sets it instead of removing the row, and find queries automatically exclude soft-deleted records.

Question 5

What is the N+1 query problem in TypeORM, and how is it solved?

Accepted Answer

Loading N related entities with N separate queries instead of 1 JOIN — solved with eager loading or QueryBuilder joins

Answer

N+1 occurs when fetching a list of N entities and then loading each one's relation separately; use eager relations or explicit JOIN in QueryBuilder to fetch everything in one query.

NestJS Practice Test

NestJS Practice Test

NestJS NestJS Database Integration & ORMs 2