This is a 2018 internet-connected app, not a 1985 GSM network.
1 billion 100 Byte messages sums up to an almost trivial 100GB. This might be a technical challenge for the neighborhood's web admin but not for any real company.
That wasn't the point at all. You were sneering at others because you had converted the numbers into GB/s and those numbers looked small, but the only foolishness was doing the conversion in the first place and the only person doing it was you. A billion messages of any size is nothing to sneeze at. Have you ever worked on a system that handled that many messages in its entire lifetime, let alone a single day?
P.S. There's no such thing as a 1985 GSM network. That phrase just makes your comment look even sillier.