they can easily go into the hundreds of TB, depending on your platform.
and i might add: i vividly remember gitlabs article how they have had automated backups and test restores for years, but when they actually needed them... it turned out some data wasn't part of it after all. just because youre testing your restore procedure doesnt mean you've actually accomplished anything.
If your restores are too time consuming to test regularly, they sure as shit aren't going to be useful in a disaster.
A newspaper that doesn't publish for a few days might recover. A bank that drops off the Swift network for days isn't a bank any more.
Banks regularly close for multiple days for bank holidays. Unscheduled downtime is a somewhat different story, though.
Luckily, the traditional SWIFT/banking infrastructure is so negligible these days, my phone can host a classic banking infrastructure for an entire small country.
A bank exists not as an isolated entitity, but as a node in a local, regional and global network of transactions.
Your phone as a “classic banking infrastructure” (nonsense phrase) can’t do credit card acquiring or realtime transactions because it’s not connected to the payment rails, transaction switches and so on (like SWIFT but all of the other less global ones run by central banks and private entities).
In developed societies, instant settlement for bank-bank transfers is the norm, and cash flow is dependent on that.
Russia and Iran pay about 2-5% for above-board (non-sanctioned) cross border transactions due to their extra costs of not being in SWIFT and USD sanctions, and between 20-50% where physical middle-people are needed to move pallets of USD.
"daily test restore is infeasible for anything but toy projects. "
It probably depends on what you call "toy" project. If you work for Google, yes I think everything is a toy project, and you're right. I only worked for ~$200M ARR/1M DAU businesses and restoring was no problem. From your point working for a FAANG business it's a toy project I can see that. But there are many more "toy projects" of this kind than FAANG companies.
"10+TB backup for example, and thats a _tiny_ backup size for a b2c product."
Sure.