A Codeigniter developer designs and develops web applications using the Codeigniter framework. Their role involves creating efficient, testable, and reusable PHP modules, solving complex performance problems and architectural challenges, and integrating user-facing elements developed by front-end developers. They also ensure the performance, quality, and responsiveness of applications, collaborate with the team to define and design new features, and identify and correct bottlenecks and bugs. Furthermore, they stay up-to-date with industry trends and emerging technologies, and assist in the entire application lifecycle, focusing on coding, debugging and troubleshooting.