SharePoint has extensive capability for bringing in datasets from external sources, such as Business Connectivity Services (BCS). BCS allows you to connect to remote data sources and bring that data in as an external list or an external data column, depending on how you want to display the data. BCS, depending on the data source you're connecting to, can support all of the standard data operation types (Create, Read, Update, Delete, and Query, otherwise known as CRUDQ operations). BCS may also have the option of modifying the data only in presentation form in SharePoint Online or the ability to synchronize the changes back to the on-premises data source.

From a development perspective, there are several coding, security, and access practices to take into consideration:

• Creating SharePoint Framework client-side solutions and web parts
• Using Azure Active Directory security when accessing APIs
• Firewall and networking requirements for connected applications to ensure minimal surface exposure
• Creating a SharePoint hybrid connectivity-based add-in
• Following best practices around client rendering and data caching to minimize round trips to data sources

There are many resources available to help guide those decision-making processes. While coding and development practices are outside the scope of the MS-300 exam, for more information on some of the line of business application development samples Microsoft has made available, you can refer to https://docs.microsoft.com/en-us/sharepoint/dev/scenario-guidance/line-of-business-integration.