A client requires downloading a CSV file from an AWS S3 bucket on a scheduled...

In Adobe Campaign Classic, an External Account is the correct component for connecting to an external data source like AWS S3:

External Account:This configuration allows Adobe Campaign to interact with external systems via protocols such as SFTP, HTTP, or cloud storage services like AWS S3. For this scenario, the developer would set up an External Account with the AWS S3 connection details, enabling scheduled file downloads directly from the S3 bucket.

By configuring an External Account, the workflow can seamlessly connect to the AWS S3 bucket and retrieve the CSV files for processing and updating the custom schema in Adobe Campaign.