What tool should an architect recommend for migrating approximately 10 million contact records into a new Salesforce environment?

The recommended tool for migrating approximately 10 million contact records into a new Salesforce environment is Salesforce Data Loader. This application is particularly suited for handling large volumes of data, making it an optimal choice for migrating extensive datasets like contact records. Data Loader is capable of processing thousands of records in batch, which is essential when dealing with such a significant number of entries.

Moreover, it supports various operations such as Insert, Update, Upsert, and Delete, providing flexibility in how data is managed during migration. The tool can also handle complex data transformations and allows for the loading of both standard and custom objects, which is crucial in a diverse data environment.

In contrast, while the Data Import Wizard can handle smaller data imports and is user-friendly, it is more limited in the number of records it can process at a time compared to Data Loader. The Excel connector, while useful for real-time data manipulation, is not designed specifically for bulk data migration and would struggle with the volume in question. Salesforce Workbench is a powerful tool for interacting with Salesforce data through API calls, but it requires a deeper understanding of how to structure queries and manage data load limits effectively, making it less straightforward for mass data migration tasks.