It is important to avoid canceling an interview unless absolutely necessary, as employers will likely consider it unprofessional and disrespectful. Unless something unexpected comes up, such as a family emergency or illness, you should ensure you still attend the interview when given the opportunity. In these situations, you must inform the employer quickly and apologize for the inconvenience instead of no-showing. This allows them to fill your spot if need be while still maintaining some goodwill between both parties.

If you must reschedule an interview, be upfront about why and provide as much information as possible so the employer knows what to expect on the new date. Even if they understand your situation, try to grant them some time to prepare for your 'makeup' appointment - at least one week should suffice. After all, not every company has jobs available all year round - missing this opportunity could mean waiting until their hiring process opens again for a chance at employment.

More info: What is Platform as a Services (PaaS)