Use build cache providers

Accelerate local development by caching and reusing builds from a provider.

Build caching is an experimental feature that speeds up npx expo run:[android|ios] by caching builds remotely, based on the project fingerprint. When you run npx expo run:[android|ios], it checks if a build with a matching fingerprint exists, then downloads and launches it rather than compiling it again. Otherwise, the project is compiled as usual and then the resulting binary is uploaded to the remote cache for future runs.

Using EAS as a build provider

To use the EAS Build provider plugin, start by installing the eas-build-cache-provider package as a developer dependency:

Then, update your app.json to include the buildCacheProvider property and its provider under experiments:

{
  "expo": {
    ...
    "experiments": {
      "buildCacheProvider": "eas"
    }
  }
}

You can roll your own cache provider by exporting a plugin that implements the following methods:

type BuildCacheProviderPlugin<T = any> = {
  /**
   * Try to fetch an existing build. Return its URL or null if missing.
   */
  resolveBuildCache(props: ResolveBuildCacheProps, options: T): Promise<string | null>;

  /**
   * Upload a new build binary. Return its URL or null on failure.
   */
  uploadBuildCache(props: UploadBuildCacheProps, options: T): Promise<string | null>;

  /**
   * (Optional) Customize the fingerprint hash algorithm.
   */
  calculateFingerprintHash?: (
    props: CalculateFingerprintHashProps,
    options: T
  ) => Promise<string | null>;
};

type ResolveBuildCacheProps = {
  projectRoot: string;
  platform: 'android' | 'ios';
  runOptions: RunOptions;
  fingerprintHash: string;
};
type UploadBuildCacheProps = {
  projectRoot: string;
  buildPath: string;
  runOptions: RunOptions;
  fingerprintHash: string;
  platform: 'android' | 'ios';
};
type CalculateFingerprintHashProps = {
  projectRoot: string;
  platform: 'android' | 'ios';
  runOptions: RunOptions;
};

A reference implementation using GitHub Releases to cache builds can be found in the Build Cache Provider Example.

Creating a custom build provider

Start by creating a provider directory for writing the provider plugin in TypeScript and add a provider.plugin.js file in the project root, which will be the plugin's entry point.

{
  "extends": "expo-module-scripts/tsconfig.plugin",
  "compilerOptions": {
    "outDir": "build",
    "rootDir": "src"
  },
  "include": ["./src"],
  "exclude": ["**/__mocks__/*", "**/__tests__/*"]
}

import { BuildCacheProviderPlugin } from '@expo/config';

const plugin: BuildCacheProviderPlugin {
  resolveBuildCache: () => {
    console.log('Searching for remote builds...')
    return null;
  },
  uploadBuildCache: () => {
    console.log('Uploading build to remote...')
    return null;
  },,
};

export default plugin;

// This file configures the entry file for your plugin.
module.exports = require('./provider/build');

{
  "expo": {
    ...
    "experiments": {
      "buildCacheProvider": {
        "plugin": "./provider.plugin.js"
      }
    }
  }
}

Passing custom options

To inject custom options to your plugin you can use the options field and it will be forwarded as the second parameter of your custom functions. To do so modify the buildCacheProvider field in example/app.json as shown below:

{
  "expo": {
    ...
    "experiments": {
      "buildCacheProvider": {
        "plugin": "./provider.plugin.js",
        "options": {
          "myCustomKey": "XXX-XXX-XXX"
        }
      }
    }
  }
}