I’m still thinking about whether I want to get AWS (Amazon”s cloud platform) certified.  But one question I had was about where I would have to go to take the exams.
In the past I’ve taken exams, and familiar with testing centers like Sylvan (Prometric), Vue, and 2Test and others.

Question: Are AWS exams online or at a testing center?
Answer: You go to a testing center to take the exam.

Question: How do you find the testing centers for AWS exams in your city?
Answer: Start the scshedule an exam process, identify the exam centers, then close the process if you just wanted to check the locations.

From this page: https://aws.amazon.com/certification/our-certifications/  click “Schedule an exam”.
You have to sign up with https://webassessor.com/wa.do?page=createAccount&branding=AMAZON and pretend you want to take an exam, just to see the exam locations and addresses.  You can then back out.

An example of Texas exam centers, such as Dallas And Austin can be seen in the image below (Dallas is highlighted). One of them is Sylvan, the other is “Business Communication Solutions”.  Those seem to be popular in major cities, along with many college campuses.