An ArcServer developer is responsible for designing, developing, and implementing web applications using ArcGIS Server, a platform for sharing geospatial data in a centralized manner. They work with geodatabases, manage server-side configurations, and ensure data integrity and security. They also develop and optimize geoprocessing and map services, and integrate them into web or mobile applications. They work closely with other developers and stakeholders to understand requirements, troubleshoot issues, and provide solutions. Additionally, they may provide technical support, create documentation, and stay updated with the latest GIS technologies. It's essential for them to have strong problem-solving skills and knowledge in GIS concepts and tools.