Build Queues on Vercel

When multiple deployments are started concurrently from code changes, Vercel's build system places deployments into one of the following queues:

• Concurrency queue: The basics of build resource management.
• Git branch queue: Understanding how builds to the same branch are managed.

This queue manages how many builds can run in parallel based on the number of concurrent build slots available to the team and user. If all concurrent build slots are in use, new builds are queued until a slot becomes available.

Concurrent build slots are the key factor in concurrent build queuing. They control how many builds can run at the same time and ensure efficient use of resources while prioritizing the latest changes.

Each account plan comes with a predefined number of build slots:

• Hobby accounts allow one build at a time.
• Pro accounts support up to 12 simultaneous builds.
• Enterprise accounts can have custom limits based on their plan.

When multiple builds are pushed to the same Git branch, they are handled sequentially. If new commits are pushed while a build is in progress:

1. The current build is completed first.
2. Queued builds for earlier commits are skipped.
3. The most recent commit is built and deployed.

This ensures that only the latest changes are deployed, reducing unnecessary builds and improving deployment efficiency.

It's possible for builds to be affected by both queues simultaneously. For example, if your builds are queued due to no slots being available and you submitted multiple commits to the same branch, the following will happen:

• The latest commit to that branch will start building when a slot becomes available.
• All previous commits to that branch will be skipped when that happens.