MongoDB live at Craigslist` is a significant milestone for MongoDB as it has successfully deployed its NoSQL database on one of the most popular online marketplaces, `Craigslist`. The deployment was driven by the need to improve data storage and retrieval efficiency, particularly with regards to schema changes and handling large amounts of unstructured data. With over 5 billion documents to be stored, the `Craigslist` MongoDB cluster is a substantial undertaking that showcases the scalability and performance capabilities of the database. The use of replica sets and sharding enables the system to handle high traffic and ensure data availability, making it an attractive solution for large-scale applications. Jeremy Zawodny, a key figure in the deployment, highlights the importance of thinking differently about indexing and bookkeeping when transitioning from relational databases like MySQL.