More informations on: https://lanbugs.de/howtos/python-co/powerdns-mongodb-backend/
The schema for the collection in mongoDB is:
for SOA record:
... { "name":"example.org", "type":"SOA", "content":"", "ttl": 300, "primary": "ns1.example.org", "mail": "admin.example.org", "serial": 2018030311, "refresh": 86400, "retry": 7200, "expire": 3600000, "nttl": 3600 } ...
for all other records:
... { "name":"www.example.org", "type":"A", "ttl": 300, "content": "1.1.1.1" } ...