This sounds like a challenge but also fun if you get it solved.
Let me know if the procedures in APOC for loading from relational databases and XML are helpful for you.
There are a bunch of talks that I linked in other places on this topic, that might be interesting to you:
Can the below query works if I have 33 million data which output using multiple join queries...
CALL apoc.load.jdbc('jdbc:derby:derbyDB','SELECT * FROM PERSON WHERE AGE > 18')
Sure, you just want to wrap the apoc.load.jdbc thing into an apoc.periodic.iterate with he 2nd statement doing the updating. Best ask in #neo4j-graph-platform:procedures-apoc