One of the mechanisms to pull data in from other systems is to go for a Product called Salesforce Data Pipeline. It is its own SKU so you need to review licensing requirements with your CSM.
It's a simple tool to connect to any external Data Store and pull data in using the Analytics Data Manager. YOu need to create a recipe to pull data in. It's super easy and lot convenient if you have many needs to get data from external systems.
You can pull data in and store it in a Staging table and process it from there.
