Heads up: I'm a node.js backend developer with an extensive IoT experience so disregard the rest if Java is a disqualifying requirement.
Hi I currently work with a startup that deploys IoT devices to monitor environmental factors like air quality and TP/RH across a wide range of locations. For that system, I have designed, developed, deployed and support a custom IoT platform hosted on AWS the distributed devices - more than 5000 at the moment - we use a Node.js based MQTT broker. I have also used the new AWS IoT service for smaller scale deployment and internal tests and I'm confident that I will be able to provide you a robust, flexible and maintainable solution for this project.
Project duration and overall cost will depend on the scope the project once you share additional details.
Looking forward to hearing from you.
Thanks,
Anani