Most ATS users are savvy enough to perform Boolean searches, meaning combining keywords. If the employer wants someone with project management, technology and quality assurance skills, it could use a search like this:

" 'project management' AND technology AND 'quality assurance' "

Only rsums that have all three exact search terms would be returned.

ATS systems are pretty smart. Keywords must be used in the proper context or the ATS might ignore the resume. And job seekers must use keywords throughout the resume , especially if their job search is in the technology industry.