Between Google IO 2015 and now, April 2016, there was a change on topics: No more limitations of subscribed devices! Before it was limited to 1 million

This change means, we can auto register each android device to one topic (e.g. /topics/VARIANT_ID),

On the server side, after I looked at how topics work, I noticed the 'conflict' with alias or any other criteria. My understanding is that, for now, we just use GCM topic only if nothing else, than the category is provided to the RESTful Sender API.

We could extend our Device Group feature, and kinda group all devices to a users group, and have the category play in there too. E.g. have some groups like:

• matthias_football
• matthias_music

but the sending here, would be a message to a device group, not a category