The order of language selection on the site and the booking pages - the person's choice, then the region, then the browser language. Why the region ranks above the browser and how we learn it.
Checking that "the time is free" and saving the booking are two separate actions, and a second booking can slip in between them. How a database-level lock closes that gap for the CRM, online booking and the calendar at once.
Why a person chooses the booking page address rather than the system, which words are reserved, why the check answers only "yes" or "no", and why the address cannot be changed.
A note on how the Telegram reminder channel is built - why there is one bot for the platform, what is inside the subscription link, and why its signature is so short.
