Regardless of the pricing option you choose, our system allows having only one active project per store at a time. When you submit a project, only after it is done and you mark it as completed, you will then be able to submit the next project.
Our system is set up in this way, in order to avoid having two or more developers working on the same store at the same time, as it could cause errors or even data loss.
Check the article below for more details about drafted project.