Custom Connector - Microsoft SharePoint & Power Apps

We need some procedures in .net (preferably c#) that we can deploy in Azure Functions to perform CRUD operations on very large sharepoint online lists (over 100,000 records in some cases). Most of the operations must be able add, remove or update records in bulk (eg. delete 1200 records from a list based on a series of parameters; or add 400 new records to a lists by copying records from another list).