The Explaination of forRoot and ForFeature

forRootAndForFeature.md

ForRoot

This is useful when the registerAs is required across, so it is best to use it in the AppModule

import databaseConfig from './config/database.config';
@Module({
  imports: [
    ConfigModule.forRoot({
      load: [databaseConfig],
    }),
  ],
})
export class AppModule {}

the registerAs has to be loaded into the configureModule.forRoot by adding it in the the load array.

ForFeature

This is valuable to ensure the registerAs is only applicable for the module only. It is better as most of the config is required for the respective modules only.

import { Module } from '@nestjs/common';
import { ConfigModule } from '@nestjs/config';
import databaseConfig from './database.config';

@Module({
  imports: [ConfigModule.forFeature(databaseConfig)],
  providers: [],
  exports: []
})
export class CouchdbModule { }

The best explanation, really yes!