A Microsoft Azure DocumentDB developer primarily designs, develops, and manages NoSQL databases on the Azure platform. They work with JSON and JavaScript directly within the database engine to ensure optimal performance and scalability. Their responsibilities include creating data models, managing data distribution, partitioning, and indexing, as well as implementing security protocols, troubleshooting issues, and ensuring high availability of data. They also use Azure's SQL API to interact with the data and may integrate DocumentDB services with other Azure products or third-party applications. Their ultimate goal is to provide efficient and effective data management solutions.