Patent Examiners do specialize in their fields. It isn't something that is just a common pool subject to any patent that comes into the pipe.

From the USPTO[1]

What kind of degree do I need to apply, and which vacancy do I need to apply to? The minimum degree required to be a utility patent examiner is a bachelor’s degree. There are dozens of STEM-related bachelor’s degree types that qualify, even if they are not the exact discipline listed in the title of the job vacancy.

For example, professionals with bachelor’s degrees ranging from engineering, mathematics, astronomy, space science, geophysics, oceanography, or hydrology could all apply to the "Patent Examiner (Physics)" vacancy when it is open. To see more details about which degrees best fit with which patent examiner vacancies, view this chart[1]. You can also attend one of our upcoming webinars or office hours to chat with a current patent examiner, or email us at JoinUSPTO@uspto.gov with your specific question.

[1] https://www.uspto.gov/jobs/become-patent-examiner [2] https://www.uspto.gov/sites/default/files/documents/patent-e...