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# NestJS Platform Fastify
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The NestJS Platform Fastify package provides a Fastify-based HTTP adapter for the NestJS framework, enabling developers to leverage Fastify's high-performance HTTP server as an alternative to Express. It offers seamless integration with NestJS applications through adapters, decorators, and interfaces while maintaining the framework's architectural patterns and providing access to Fastify's superior performance characteristics.
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## Package Information
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- **Package Name**: @nestjs/platform-fastify
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- **Package Type**: npm
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- **Language**: TypeScript
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- **Installation**: `npm install @nestjs/platform-fastify`
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## Core Imports
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```typescript
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import { NestFactory } from '@nestjs/core';
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import { FastifyAdapter, NestFastifyApplication } from '@nestjs/platform-fastify';
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```
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For individual components:
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```typescript
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import { 
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  FastifyAdapter,
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  NestFastifyApplication,
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  RouteConfig,
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  RouteConstraints,
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  RouteSchema,
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  FASTIFY_ROUTE_CONFIG_METADATA,
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  FASTIFY_ROUTE_CONSTRAINTS_METADATA,
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  FASTIFY_ROUTE_SCHEMA_METADATA
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} from '@nestjs/platform-fastify';
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```
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## Basic Usage
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```typescript
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import { NestFactory } from '@nestjs/core';
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import { FastifyAdapter, NestFastifyApplication } from '@nestjs/platform-fastify';
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import { AppModule } from './app.module';
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import * as path from 'path';
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async function bootstrap() {
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  try {
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    // Create NestJS application with Fastify adapter
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    const app = await NestFactory.create<NestFastifyApplication>(
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      AppModule,
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      new FastifyAdapter()
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    );
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    // Enable CORS if needed
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    app.enableCors();
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    // Serve static assets
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    app.useStaticAssets({
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      root: path.join(__dirname, '..', 'public'),
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      prefix: '/public/',
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    });
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    // Listen on port 3000
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    await app.listen(3000);
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    console.log('Application is running on: http://localhost:3000');
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  } catch (error) {
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    console.error('Error starting the application:', error);
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    process.exit(1);
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  }
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}
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bootstrap();
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```
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## Architecture
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The NestJS Platform Fastify package is built around several key components:
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- **FastifyAdapter**: Core HTTP adapter that bridges NestJS and Fastify, handling request/response lifecycle
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- **Route Decorators**: Specialized decorators for Fastify-specific route configuration, constraints, and schema validation
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- **Application Interface**: Enhanced NestJS application interface with Fastify-specific methods
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- **Type Integration**: Full TypeScript support with generic server, request, and response types
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- **Plugin System**: Direct access to Fastify's plugin ecosystem through the adapter
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## Capabilities
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### HTTP Adapter Integration
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Core adapter functionality for integrating Fastify with NestJS applications. Provides lifecycle management, middleware support, and request/response handling.
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```typescript { .api }
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class FastifyAdapter<
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  TServer extends RawServerBase = RawServerDefault,
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  TRawRequest extends FastifyRawRequest<TServer> = FastifyRawRequest<TServer>,
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  TRawResponse extends RawReplyDefaultExpression<TServer> = RawReplyDefaultExpression<TServer>,
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  TRequest extends FastifyRequest<RequestGenericInterface, TServer, TRawRequest> = FastifyRequest<RequestGenericInterface, TServer, TRawRequest>,
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  TReply extends FastifyReply<RouteGenericInterface, TServer, TRawRequest, TRawResponse> = FastifyReply<RouteGenericInterface, TServer, TRawRequest, TRawResponse>,
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  TInstance extends FastifyInstance<TServer, TRawRequest, TRawResponse> = FastifyInstance<TServer, TRawRequest, TRawResponse>
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> extends AbstractHttpAdapter<TServer, TRequest, TReply>
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interface FastifyAdapterConstructorOptions<
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  Server extends RawServerBase = RawServerDefault,
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  Logger extends FastifyBaseLogger = FastifyBaseLogger
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> extends FastifyServerOptions<Server, Logger> {
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  skipMiddie?: boolean;
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}
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```
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[HTTP Adapter](./fastify-adapter.md)
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### Route Configuration Decorators
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Specialized decorators for configuring Fastify-specific route behavior including constraints, schema validation, and configuration options.
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```typescript { .api }
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function RouteConfig(config: any): MethodDecorator;
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function RouteConstraints(config: RouteShorthandOptions['config']): MethodDecorator;
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function RouteSchema(schema: FastifySchema): MethodDecorator;
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```
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[Route Decorators](./decorators.md)
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### Application and Configuration Interfaces
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Enhanced interfaces for NestJS applications with Fastify-specific functionality and configuration options for static assets, view engines, and body parsing.
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```typescript { .api }
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interface NestFastifyApplication<TServer extends RawServerBase = RawServerDefault> 
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  extends INestApplication<TServer> {
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  getHttpAdapter(): HttpServer<FastifyRequest, FastifyReply, FastifyInstance>;
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  register<Options extends FastifyPluginOptions = any>(
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    plugin: FastifyPluginCallback<Options> | FastifyPluginAsync<Options> | Promise<{ default: FastifyPluginCallback<Options> }> | Promise<{ default: FastifyPluginAsync<Options> }>,
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    opts?: FastifyRegisterOptions<Options>
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  ): Promise<FastifyInstance>;
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  useBodyParser<TServer extends RawServerBase = RawServerBase>(
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    type: string | string[] | RegExp,
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    options?: NestFastifyBodyParserOptions,
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    parser?: FastifyBodyParser<Buffer, TServer>
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  ): this;
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  useStaticAssets(options: FastifyStaticOptions): this;
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  enableCors(options?: FastifyCorsOptions): void;
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  setViewEngine(options: FastifyViewOptions | string): this;
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}
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```
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[Interfaces and Configuration](./interfaces.md)
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## Types
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### Core Types
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```typescript { .api }
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type NestFastifyBodyParserOptions = Omit<Parameters<AddContentTypeParser>[1], 'parseAs'>;
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// Metadata constants for decorators
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const FASTIFY_ROUTE_CONFIG_METADATA: string;
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const FASTIFY_ROUTE_CONSTRAINTS_METADATA: string;
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const FASTIFY_ROUTE_SCHEMA_METADATA: string;
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```
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### Server Type Options
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The adapter supports various Fastify server configurations:
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```typescript { .api }
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type FastifyHttp2SecureOptions<
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  Server extends http2.Http2SecureServer,
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  Logger extends FastifyBaseLogger = FastifyBaseLogger
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> = FastifyAdapterBaseOptions<Server, Logger> & {
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  http2: true;
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  https: http2.SecureServerOptions;
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};
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type FastifyHttp2Options<
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  Server extends http2.Http2Server,
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  Logger extends FastifyBaseLogger = FastifyBaseLogger
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> = FastifyAdapterBaseOptions<Server, Logger> & {
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  http2: true;
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  http2SessionTimeout?: number;
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};
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type FastifyHttpsOptions<
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  Server extends https.Server,
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  Logger extends FastifyBaseLogger = FastifyBaseLogger
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> = FastifyAdapterBaseOptions<Server, Logger> & {
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  https: https.ServerOptions;
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};
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type FastifyHttpOptions<
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  Server extends http.Server,
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  Logger extends FastifyBaseLogger = FastifyBaseLogger
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> = FastifyAdapterBaseOptions<Server, Logger> & {
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  http: http.ServerOptions;
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};
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```