Hi Tod,
Thanks for reaching out.
MongoDB Mobile Sync can be used offline, but right now, it's only possible to interact with the local offline version of the collection if you are logged in as a user. To log into a user, you need to have been online at one point. Once you are logged in, you can go offline and interact with the local database whether you are offline or online.
If you need to interact with the database when you are offline and signed out, you can currently only do that with the local MongoDB service, which lets you interact with a local collection in an offline-only way. You can store documents in this local collection, and you can write code to move these documents over to your mobile sync collection when you are signed in.
Would this fit your use case? Let us know if you have any further questions.
Thanks,
Adam