What is the maximum number of connections node.js can support to different mysql databases?

Question

MySQL

Greetings, I ran into such a problem: It is
required to make many connections with different mysqls within one node.js thread.
It would be desirable to know in what limit of constant supported connections and what total limit of requests can be in these .
In practice, it looks like this:
There is a project on which they did it for the customer.
After the release, the customer wanted to sell the application as a service using one physical server with one node process for all clients. This assumes the allocation of one database for each client.
What is the calculation methodology and what to read on this topic?