They even said as much in TFA - "[...] overkill, yes we know, but to be fair we had AWS credits".

Fully acknowledging the irony I am about to invoke - this is why I hate startup culture. Not startups, but this ridiculous culture of "well the VC gave us a million bucks and that bought us $100,000 in AWS credits, so let's just use it."

As someone who has built my company fully on my own dime (and the dimes of two colleagues), it's easy enough to burn piles of money in AWS (or any other cloud) when you're making an attempt at being judicious. Spinning up eight backends (edit: running five instances each, no less!) just because you have money, despite the fact that you know you don't need that much compute, is just insane. If for no other reason than you're just throwing your own credits away.

If I give them a trampoline they shouldn't spend all day jumping on it, just because they can. Especially if they're busy with features.

They literally had 1 instance of the backend per $1 of revenue, and the reason the bug wasn't seen straight away was because they had 40 backend instances each with a single uuid that could be used for users before it broke with non-unique id errors.