Kuaidi, China's largest car service application, relies on MongoDB at the heart of its taxi hailing service to connect drivers with passengers up to 6 million times a day and manage nearly half a billion orders. The company has scaled MongoDB across four geographic regions, serving thousands of reads and writes every second, and uses it as an active archive for storing order data. Kuaidi considered other databases but found MongoDB to meet its performance, scalability, and ease-of-use objectives, making it the best choice for their application. Their MongoDB deployment is geo-distributed, with a 7-node replica set in each region, allowing for low latency access and scalability. The company serves 50,000 operations per second and has grown to over half a billion documents, continuing to scale. Kuaidi plans to migrate other applications to MongoDB as well, including their marketing team's promotions and messaging database. The company is looking forward to the forthcoming MongoDB 3.0 release's document level concurrency control feature. Ouyang Kang, Chief Architect at Kuaidi, advises others considering using MongoDB to test it with their app, queries, and data to ensure choosing the right technology for their next project.