Suppose that I have 3 databases in my odoo community instance db1, db2 and db3, hosted on-premise (AWS)

I want to link these databases to my subdomains. for example:

paris.example.com will link to db1

london.example.com will link to db2
toronto.example.com will link to db3

How can I do that? I can use nginx or something else. If there is some nice documentation or a recommendation for a similar approach, I will appreciate that.