What are the answers to questions on logic (barbershop and database)?

Question

Database

Hello, I was recently at an interview and came across the following two questions that I could not answer, but the answer to them would be extremely interesting to me.

1. There are two databases that store information about customers. The same client is registered in both databases: in the first as "Igor", in the second as "Igor". It is required to load the client data into the store and use only the "correct" record.

2. There are 600 thousand people in the city of N, how many hairdressers are needed in the city so that there are no queues?

Answer 1

1. "Igor", that is, it will also have the second option.
2. 600 thousand, since anyone can start a haircut at any time. Or 300 thousand if the hairdresser agrees that another master would work behind his chair (additional question),