Hiring a MongoDB developer can be crucial for managing your database systems effectively. They can handle large amounts of data, offering high performance, scalability, and flexibility. MongoDB developers are adept at using this NoSQL database, which is schema-less and can store structured and unstructured data. It is particularly useful for applications with data that doesn't fit neatly into a table. MongoDB's horizontal, scale-out architecture can easily accommodate your growing data. Additionally, MongoDB developers can help you leverage the database's speed and efficiency, making your applications more responsive and improving the overall user experience.