QR on a brick wall outside a secret bar. Daily-rotating password + a 40-scan-per-night cap. Past the limit, late arrivals see 'come back tomorrow.'
The password changes every day and is given to guests via Telegram. Once 40 guests have scanned through, the QR auto-redirects everyone else to a 'fully booked' page — capacity control without a paid host on the door.
Free tier includes 1 permanent QR and the recovery key — upgrade the slot with the exact modules this case uses whenever you need them.