MLM (network marketing and all that), how best to make a "transfusion"?

Question

PHP

Good day.
I wrote a multi-level referral system without restrictions on people, but now I need a matrix one..

matrix example

How to make a "transfusion" of users.
For example, a person comes in via a ref link to id-1, but he already has 3 referrals and he cannot accept more, how to assign him to the next person (the one who invited id-1) lower in the hierarchy? Provided that he has free "places".
There are a lot of if and queries to the database in my head, but from the side of load and optimization it seems to me a bad solution. The customer has plans for a load of at least 3k people or more in a marketing progression..

Answer 1

There are a lot of if and queries to the database in my head, but from the side of load and optimization it seems to me a bad solution.
recursion
explain to him that more people - more costs for the system