UPDATE: December 2018
After one year of testing, we have decided to shut down the beta of Sandboxes. Using the feedback that we gathered, we are currently working on a new and improved version of the test environment feature. Make sure to follow us on Twitter for news and updates on the release date.
Sandboxes act as stage servers, allowing you to run your application from a chosen branch with just one click.
Every time you make a push to this branch, the application is rebuilt and run afresh. It's a great solution for stage branches because the sandbox will always serve the newest code version.
However, it's not a perfect choice for branches to which commits are made really often. When new changes are commited, the sandbox is not available so you cannot work on it.
From now on, you can set the Manual mode in your sandbox and rebuild it only when you want to:
On the sandbox list you can see whether the sandbox serves the newest version of the branch or if it's out of date:
You can see it in the sandbox view in the upper right corner as well: