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Response Headers

Response Headers


The Middleware Response Headers extension enables the addition of custom response headers, which can be particularly useful for managing application caching or establishing security rules.

With this extension, you can overwrite or set headers for individual API methods or apply them globally across your application. It can be implemented for any Unified Alokai backend, and third-party tool integration.

How it works?

The extension can be used in two ways:

  • Locally: to set custom headers for individual API methods
  • Globally: to set Cache-Control header for all the API methods

Internally, the extension will identify all GET-type methods and add/overwrite the headers to their responses using the afterCall hook. Read the Middleware Extensions guide to learn more about the internals of an extension.


To install the extension, run the following command in your apps/storefront-middleware folder:

yarn add @vsf-enterprise/middleware-headers


To configure the extension for a specific integration, add the following code to your middleware.config.js file:

import headersExtension from '@vsf-enterprise/middleware-headers';

import { extensionConfig } from './extensionConfig';

export default {
  integrations: {
    // ... other integrations
    [integrationName]: {
      extensions: (extensions: ApiClientExtension[]) => [
        headersExtension({ ...extensionConfig }),
        // ... other extensions


Local Usage

Now, in the extensionConfig.ts file, you can set up your headers for individual API methods.

export const extensionConfig = {
  methods: {
    [apiMethodName]: {
      response: {
        headers: {
          'Cache-Control': 'your-rules',
          // ... other headers

Here, your IDE will be able to suggest the available API methods and their names. You can also define your custom ones, making sure that the method name matches the one from the API.

To provide proper types inference you can use generic type to define them, like this.

headersExtension<'fooMethod' | 'barMethod'>({ ...config }),

Global Usage

To apply global Cache-Control rules on every API method, you can set the cacheControl property in your extension's configuration.

export const extensionConfig = {
  cacheControl: 'your-rules',

The extension also ships with a predefined cacheControlRules value. You can opt-in to using this by setting cacheControl to true.

/* This is just for presentation purposes; the code is part of the package internals. */

const SHORT_TTL = 60 * 5; // One hour
const cacheControlRules = `public, max-age=0, s-maxage=${SHORT_TTL}, must-revalidate`;
export const extensionConfig = {
  cacheControl: true,


function extension<T extends string>(
  config?: ExtensionConfig<T>
): ApiClientExtension;