Migrating Terabytes of IoT Data From a Legacy NoSQL Database to MongoDB Atlas With MongoDB's Custom Migration Tool` discusses how a large European energy company, with 7.6 million smart meters, migrated its legacy NoSQL database to MongoDB Atlas to handle the massive influx of data from IoT devices. The company faced challenges such as scalability issues, increasing costs, and poor performance on its current system. To address these challenges, they decided to migrate to MongoDB Atlas using a custom migration tool developed by their technical partner PeerIslands. The migration was complex due to the large volume of data and uneven write loads, but the custom tool successfully handled these challenges with minimal downtime. After the migration, the company has experienced improved performance, reduced costs, and is better equipped to handle business needs, leveraging MongoDB's time-series capabilities for IoT functionality.