[strken]

"Absolutely sure" isn't an achievable level of surety, because everything has a chance of failure, however small.

You could go for "NASA sure", which is when you spent 100x the effort of the average tech company making sure only some of your spacecraft explode on launch, or you could go for "Github sure", which is when you spend a large chunk of your $200+ million ARR to ensure your core product only has a couple of major outages every year, or you could go for "startup sure", which is when your test coverage is 5% and you throw random stuff into production to see who complains, but you can't ever achieve "absolutely sure".

[hhmc]

It's worth noting that you can absolutely apply every level of "sureness" within the same company - and such gradation can be very effective if applied smartly.