Each Google Cloud Platform project is granted quota to run ten builds at a time. When this quota is filled, requests for additional builds are queued and processed serially after the running build completes.
From time to time, Cloud Build might allow more than ten concurrent builds per project, but users should not expect this behavior and should design their use within the quota limit of ten concurrent builds per project.
Google may change this restriction at any time.
A build trigger instructs Cloud Build to automatically build your source whenever there are changes pushed to the build source. You can create up to 300 build triggers per GCP project.