Using custom connectors, you can integrate your business applications in Microsoft Flow. But the idea sounds better than the reality is.
Now that your organization is using Microsoft Flow, are you sure that you set it up correctly so that it won't leak your confidential information?
Coming June 27, 2018 you will have a unique opportunity to learn how to make the best use of the latest Office 365 capabilities to design and build solutions for your organization.
If you host your APIs on Azure, secure them with Azure AD and want to use them in the SharePoint Framework, you need to setup CORS correctly.
SharePoint Framework allows you to easily test the web parts you're building in your production tenant without having to deploy them first. But are you okay with the risk it exposes your data to?