A Datastage Developer is responsible for designing, developing, and implementing ETL processes in IBM's DataStage tool. They extract data from various sources, transform it according to business rules, and load it into target databases or data warehouses. They also conduct data analysis, debugging, and troubleshooting to ensure data quality and integrity. Other duties include optimizing job performance, creating technical specifications, and providing support for data migration projects. They work closely with data analysts and other stakeholders to understand their data requirements and develop solutions accordingly. They play a crucial role in data management and decision-making processes.