Managing Concurrent Builds

With simultaneous changes to the same project or branch, your team can face delays with deployments being built when they are placed in a queue. In situations when you cannot wait for the build queue, Vercel provides the following options:

• Concurrent builds
• On-demand concurrent builds

Review Build Queues on Vercel to understand how and when builds get queued.

Generally, when you make multiple deployments in the same Vercel account, the builds get queued, and only one deployment is built at a time. Concurrent Builds allow you to build multiple deployments with Vercel simultaneously.

Team accounts allow you to increase the number of Concurrent Builds from the Billing section on the team Settings page, enabling the team to deploy faster.

You can manage the number of concurrent builds on the team Settings page, under Billing. Depending on your plan, you can edit the number of slots required for your team.

On-demand concurrent builds provides dynamic scaling of builds, allowing teams to temporarily increase their build capacity when needed. If a build gets queued due to the team reaching its concurrent build limit, on-demand concurrency allows that build to proceed.

You are charged for on-demand concurrency based on the number of 10-minute build slots required to allow the builds to proceed as explained in usage and limits.

You can apply it to a specific deployment at any time with urgent on-demand concurrent builds or enable it at the project level to avoid the concurrency queue.

You can activate on-demand concurrency for any specific build through a Start Building Now button. Regardless of the reason why this build was queued, it will proceed.

1. Select your project from the dashboard.

2. From the top navigation, select the Deployments tab.

3. Find the queued deployment that you would like to build from the list. You can use the Status filter to help find it. You have 2 options:

   • Select the three dots to the right of the deployment and select Start Building Now.
   • Click on the deployment list item to go to the deployment's detail page and click Start Building Now.

4. Confirm that you would like to build this deployment in the Start Building Now dialog.

When you enable on-demand build concurrency at the level of a project, any queued builds in that project will automatically be allowed to proceed.

You can enable it on the project's Advanced Settings page:

1. From your Vercel dashboard, select the project you wish to enable it for.
2. Select the Settings tab, and go to the Advanced section of your Project Settings.
3. Under On-Demand Concurrent Builds, toggle the switch to Enabled and save.

When Vercel queues builds, we'll processes them in chronological order (FIFO Order). If a build has to wait for queued preview deployments to finish, it can delay the production release process.

To ensure that changes to the production environment are prioritized over preview deployments in the queue, you can enable Prioritize Production Builds:

1. From your Vercel dashboard, select the project you wish to enable it for
2. Select the Settings tab, and go to the Advanced section of your Project Settings
3. Under Prioritize Production Builds, toggle the switch to Enabled

On-demand concurrent builds usage: The number of 10-minute build slots needed to allow your builds to proceed is automatically scaled based on multiple factors such as remaining time left from previous unused build slot time. For example, if one build slot was used in on-demand concurrency mode and it took 17 minutes for your deployment to build, you will be charged for two 10 minute build slots. If another build needs to bypass the queue in the same billing period, the 3 minutes left over will first be used.