Swift Backend Developer

The client is a startup from the "renewables" sector and is currently looking for a Swift developer to complement the internal dev team of four.
The "special feature" in this case is that they are using Swift for their iOS app as well as in the backend. This is why the freelancer should have several years of experience with a modern backend language (Ruby, Python, PHP, Node.js etc.) if s/he hasn't worked with Swift in the backend before.
Proven open-source work as well as knowledge with Postgres, AWS/GCP, microservices and Docker would be beneficial.
The freelancer should work 100% remotely from her/his own (home) office.