Customizing Serverless Functions

When extending your project with Serverless Functions, you might find yourself in a situation where adjusting the default behavior is necessary.

Today, we are adding a new functions configuration property to allow you to do just this.

Custom Memory & Execution Duration

In most cases, zero configuration is required to create deployments with Vercel. Every Serverless Function (in all projects created after November 8th) receives the following attributes by default:

• Memory: 1024 MB (1 GB)
• Maximum Execution Duration: 5s (Hobby), 10s (Pro), or 30s (Enterprise)

Now, you can customize these values in your vercel.json file like so:

{
	"functions": {
		"api/test.js": {
			"memory": 3008,
			"maxDuration": 10
		}
	}
}

Read more about the constraints for each property in our documentation.

Community Runtimes

When deploying Serverless Functions without configuration (using the /api directory), you can choose from a list of officially supported languages.

If the language you'd like to use is not part of this list, you can add functions to your vercel.json file to assign Community Runtimes to your Serverless Functions.

Community Runtimes are provided by a third-party, for example, vercel-php:

{
	"functions": {
		"api/test.php": {
			"runtime": "vercel-php@0.0.10"
		}
	}
}

After configuring the functions property, your api/test.php Serverless Function will be executed using the vercel-php Community Runtime.

If you are interested in using a Community Runtime or creating one yourself, check out the following documentation pages:

• List of all Community Runtimes
• Guide for creating a Community Runtime

API Changes

If you are developing applications on top of the Vercel API, you will need to use v11 of the deployment creation endpoint to take advantage of the functions property.

Conclusion

With the new functions property, you can configure the memory and maximum execution duration of your Serverless Functions, or assign a custom runtime.

This is just one of several features we are planning to launch in order to support advanced use cases of Serverless Functions on Vercel.

Let us know what you think about this change!