An Applicant Tracking System (ATS) developer designs, builds, and maintains software used by companies to streamline their recruitment process. They ensure the system can efficiently handle job postings, sort and filter resumes, and track applicants' progress. The developer must integrate the software with existing HR systems, and ensure it complies with data privacy laws. They troubleshoot issues, provide technical support, and regularly update the system to add new features or improve functionality. They work closely with HR professionals to understand their needs and make the recruitment process more efficient, accurate, and user-friendly.