This project is a rewrite of the original syncstorage project which was written in Python.
Internally at Mozilla, this work was dubbed "Durable Sync". Why Durable, you ask? It’s been named that way as the defining user benefit of this work is that we’re no longer using ephemeral storage for Sync data. Starting now we use durable (aka persistent) storage to more closely align with user’s expectations of the service; ie that Sync is not only a way to transfer data between multiple devices, but it can also be used more reliably as a way to store data from a single device.
The project has also been driven by the fact that the old syncstorage runs on Python 2.7, which was EOL’d in the beginning of 2020.
Learn a bit more about this work here on the services blog.