An ArchLinux developer is responsible for maintaining the ArchLinux distribution, ensuring its smooth running and updating it with new features, fixes, and enhancements. They write code, troubleshoot and resolve issues, and liaise with the user community to understand their needs and preferences. Developers also manage the package ecosystem, ensuring compatibility and stability, and work on improving the system's performance. They are involved in the creation and maintenance of documentation, providing clear instructions and guidelines for users. Furthermore, they collaborate with other developers, contributing to the open-source community, and staying updated with the latest developments in Linux and software technologies.