Question: how data sync works?

[pedrosimao]

I am just trying to understand how the Golang scheduler sync interact with the Node based server syncs.
If I understand right the Golang scheduler will download data in pre-determined times.
On the other hand the Node server will only sync data when the user tries to access it, and it detects it is not synched yet.
Is it correct? Or is there some extra logic that I didn't fully understand?
Could the Node server also be used to schedule syncs? Just wondering if we could simplify the codebase focusing on one programming language...