FastResponse for Deno

FastResponse is an optimized implementation of the Response constructor for Deno.serve. By bypassing spec checks, it provides quicker response times compared to the standard API.

Note: FastResponse relies on accessing internal properties. This may introduce breaking changes if the internal properties of the Deno server API change in the future.

Compatibility

It has been tested and works with Deno version 1.36.4.

Usage

import FastResponse from 'npm:fast-response';

It is intended solely as a return value for Deno.serve. Using it outside this context is not recommended and will not work.

⚠️ Caution: FastResponse does not perform any input validation. This design choice contributes to its speed, but users must ensure the safety and correctness of the data they pass into it

Constructor

new FastResponse(
  body: null | undefined | Uint8Array | string | ReadableStream,
  options?: {
    status?: number,
    headers?: Array<[string, string]> | Headers
  }
)

new FastResponse(body)

The body parameter accepts values of type null, undefined, Uint8Array, string, or ReadableStream.

const hello = new TextEncoder().encode('a'.repeat(1024));
Deno.serve({ port: 3000 }, () => new FastResponse(hello));

new Response(body, { status, headers })

Deno.serve({ port: 3000 }, () => {
  return new FastResponse('hello', {
    status: 200,
    headers: [['Content-Type', 'text/plain']] // new Headers({ 'Content-Type': 'text/plain' })
  });
});

FastResponse.json

Deno.serve({ port: 3000 }, () => FastResponse.json({ hello: 'world' }));

Unlike the standard Response object, FastResponse does not implement methods like .arrayBuffer(), .text(), .clone(), .blob() and .json(). Attempting to use these methods will result in errors.

const response = new FastResponse('body');
const buffer = await response.arrayBuffer(); // Throws an error

Performance

Using wrk with the following code

const hello = new TextEncoder().encode('a'.repeat(1024));

Deno.serve({ port: 3000 }, () => new FastResponse(hello));
Deno.serve({ port: 3001 }, () => new Response(hello));

| | Requests/sec | Transfer/sec | | --------------------------------- | :-----------: | :----------: | | new FastResponse() | 268813.99 | 288.41MB | | new FastResponse() with headers | 256938.91 | 282.04MB | | FastResponse.json() | 260490.43 | 36.77MB | | new Response() | 221667.42 | 237.82MB | | new Response() with headers | 178093.76 | 195.49MB | | Response.json() | 247716.75 | 34.96MB |

Caveats

• The usage of internal properties means this solution could break in future versions of Deno