A GitLab developer designs, codes, debugs, and maintains software applications using GitLab, a web-based DevOps lifecycle tool. They collaborate with teams to manage code repositories, handle version control, automate builds, and integrate different stages of development. They also contribute to the continuous integration (CI), continuous delivery (CD), and continuous deployment (CD) processes. GitLab developers fix bugs, improve system performance, and develop new features. They use GitLab's tools for issue tracking, code review, and testing to ensure high-quality software. Furthermore, they may assist in developing DevOps strategies, troubleshooting system issues, and providing technical support.