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@json-express/transport-fastify ​

Official Fastify transport for JSONExpress.

The @json-express/transport-fastify package implements the ITransport interface to serve your JSONExpress application using Fastify.

If your application requires extreme throughput and minimal overhead, you can swap out the default Express transport for Fastify. Because JSONExpress is completely framework-agnostic, your database adapters, schema validation, and custom endpoints remain 100% untouched.

Installation ​

bash
npm install @json-express/transport-fastify fastify @fastify/cors

Configuration ​

The transport is auto-discovered by the json-express runtime — installing the package is enough. Most users start with @json-express/boot (which ships transport-express) and switch to Fastify by uninstalling Express:

bash
npm uninstall @json-express/transport-express
npm install @json-express/transport-fastify fastify @fastify/cors
npx json-express

If both transports are installed, pick one in .env:

bash
jex.transport=@json-express/transport-fastify
jex.port=8080

Core Features ​

1. Zero-Cost Abstraction ​

Fastify is famous for being one of the fastest Node.js web frameworks available. This transport is built to stay out of the way. It maps the internal RouteDefinition arrays directly to Fastify's native fastify.route() API, ensuring you retain the full performance benefits of the underlying framework.

2. Built-in CORS ​

Unlike Express, which requires external middleware for Cross-Origin Resource Sharing, this transport integrates directly with @fastify/cors. Configure it under fastify.cors in your config provider — for object-shaped values use jex.config.ts rather than .env:

typescript
// jex.config.ts
export default {
    fastify: {
        cors: {
            origin: ['https://admin.myapp.com'],
            credentials: true
        }
    }
};

When this block is present, the transport registers and configures @fastify/cors for you.

3. Asynchronous Trace Context ​

Just like the Express transport, the Fastify transport ensures enterprise traceability. Every request is wrapped in Node.js AsyncLocalStorage, generating a unique traceId. If your schema hooks or background queue workers write to the system logger, those logs will be beautifully grouped by the HTTP request that triggered them.

4. Seamless Plugin Migration ​

One of the biggest headaches in Node.js is migrating an application from Express to Fastify, because you often have to rewrite hundreds of req and res method calls (e.g., changing res.json() to reply.send()).

Because JSONExpress strictly types custom endpoint handlers using JsonRequest and JsonResponse, you can safely swap @json-express/transport-express for @json-express/transport-fastify in package.json and deploy immediately!