Why would employers re-post a job even though they are already interviewing candidates? Is this usually a sign of a "fake" job posting?
Why would employers re-post a job even though they are already interviewing candidates?
Because they haven't yet hired someone for the job. It only makes sense to keep looking for the best candidate until you hire one.
It's the same reason you should keep interviewing with several potential employers until you are actually offered and accept a job.
How a company advertises depends on the size of the company and the type of job being advertised.
In large companies with thousands of employees many job posting look identical. They a looking for somebody to serve as X with 1-Y years of experience and a bachelors degree. Many divisions, branches, programs, projects, and teams can use people with those basic skills.
Some companies will constantly advertise some of their basic positions all the time and then grab a bunch of recent resumes when ever they need to hire. They may have enough jobs in a large city to not need to get specific about the location.
In other cases they will advertise for a position, set a closing date in a week or two, and then start the interview process right after the deadline. Then immediately run an almost identical advertisement with just a different position number.
Sometimes positions are always open because they are having trouble finding person who can fill the position. It can be for many reasons. They are having trouble getting candidates, the skill set is rare, the person making the hiring decision is unable to make a decision, or they have multiple openings.
Knowing how they advertise positions can help when applying. In the case with specific closing periods it is fine to apply to the next job opening because they are being filtered and interviewed by a different team who is looking to fill their opening. In the case where they are constantly open you might want to apply every few months to make sure you still have a fresh application in the system.