The role of a Hadoop developer is to plan, implement the infrastructure on the cloud. Hadoop developer has to handle and maintain the Hadoop applications deployed on the cloud. They also have to work with Hadoop architects, DevOps teams in case of necessary. They also have to manage the big databases and ensure the data is secure.
You can take up this course on Hadoop training by Intellipaat to become a Hadoop developer.
You can watch this video on who is a Hadoop developer to know more about the roles and responsibilities of a Hadoop certification: