I don't think we need to design the entire "can you legally drink" SaaS, hopefully my example is clear enough and people can leverage the concept for more reasonable circumstances.

Show HN: drink.ly (YC W2023), a cloud-native, B2B drinking age verification SaaS, backed by Postgres

Given that I keep getting ads on reddit about some API to predict age and gender from a given dataset of users and the OP of that ad keeps saying that it's hugely succesful, this business is practically guaranteed to succeed.

Seriously, want to make some easy money? Build this.

Until the legal drinking age changes :-)

Ideally you only verify at time of purchase and do not care afterwards until next purchase. Bare minimum to hold to laws

Ideally you also don't need to verify it more than once, though. Otherwise, it will be friction that detracts from the user experience.

That’s why you need the SAAS, for compliance and i18n!

Then it's time to flush all entries, set the column to nullable or use an enumeration and re verify everyone on the next visit

Fun fact: in some places in Canada the legal drinking age is 19

Please elaborate what is “fun” about that fact? The drinking age is 19 in most of Canada, 18 is the exception. And the drinking age varies all over the world.

It used to be between 21 in most of the US until the voting age was lowered to 18 in 1971. It was then either 18 or 19 in most states (generally the more liberal ones) until 1984 when the national minimum was passed. 19 really is sort of a sweet spot for socially liberal North America.