The full-featured stock image may be too cumbersome for some applications. Applications that require faster bootup time or a smaller root filesystem will benefit greatly from using a lighter distribution like Buildroot. To assist customers heading down this path, we maintain our own Buildroot br2-external tree that includes support for various platforms. This tree includes upstream Buildroot as a submodule, which eases updating between Buildroot releases. See the Buildroot manual for more information on Buildroot and br2-external trees.
In order to provide consistency, the Buildroot image we provide is fairly large but it includes a number of tools that are present on our stock image so that transitioning from one to the other is much easier. The Buildroot configuration could be customized to provide a much smaller footprint with a faster bootup time. Our current buildroot averages about 10 seconds of bootup time (much of this is spent on networking). Reducing the configuration can bring this time down to under 5 seconds from power on to login prompt.