Powering the 5V relay from the same 5V buck that feeds the ESP32 is fine. The buck converter simply produces a 5V rail. Any number of 5V devices (ESP32 via USB, a 5V relay module, QR module if 5V TTL, etc.) can share that rail if the buck can supply the total current simultaneously. All devices ...

Your scanner requires 12V, but the ESP32 only accepts 5V. You’ll need a buck converter (12V → 5V) to feed the ESP32 (not a USB micro adapter unless it’s rated properly). The relay must also match your logic: If it’s a 5V relay module, then power it from the buck’s 5V output.

Okay, thanks for the ...

I need to make a door lock that opens using RFID and QR. I've made a drawing and a list of where all the wires should go. Could someone help me figure out if this works, what could be improved, or what's missing?

The list:
Product specifications

ESP32 Dev Kit 4 (controller)
This controls ...