Letting a stranger contact a car owner without giving them the number
Letting a stranger contact a car owner without giving them the number There is a small, very common problem in Indian cities that turns out to be a surprisingly good systems design exercise. A car is parked badly. It is blocking a gate, a driveway, another car. Someone needs the owner to move it, right now. The traditional fix is a phone number written on a sticker on the windscreen. That works. It also means a stranger — any stranger, forever — has the owner's personal number. Why the sticker is worse than it looks Once a number is visible on a windscreen, a few things follow: It gets scraped. Numbers on vehicles end up in marketing lists. It cannot be revoked. Change your number and every sticker you own is now wrong. It has no context. A 2am call could be a genuine emergency or someone who saw the number three months ago. It is a safety issue for some owners in a way it is not for others. A number attached to a vehicle, at a known parking spot, at predictable times, is more information than most people realise they are publishing. So the requirement is oddly specific: a stranger must be able to reach the owner, immediately, without ever learning how to reach them again. That constraint is what makes this interesting. The naive version, and why it fails First instinct: put a QR code on the vehicle that opens a page with a "call owner" button, and put the number behind the button. This solves nothing. The number is still in the page source. Anyone who wants it can get it, and now you have added a scan step for the honest majority while stopping none of the dishonest minority. Second instinct: put a contact form behind the QR. The stranger types a message, the owner gets a notification. Better on privacy, useless in practice. The person needs the car moved in the next ninety seconds. They are not filling in a form and waiting for an email. If the fast path is not there, they go back to writing an angry note. The real requirement is synchronous contact with asynchron