How to check if the source of the encountered problem is DNS?

In the article on her blog, Julia Evans discusses issues related to DNS (Domain Name System) and how to diagnose problems associated with it. She explains that DNS is a critical component of Internet infrastructure, responsible for translating domain names into IP addresses, which is essential for online services to function correctly. Julia provides practical tips on approaching DNS troubleshooting, such as checking local settings, using diagnostic tools, and testing different DNS servers to determine if they are indeed the source of the problem. She also touches on the response times of DNS servers and how to optimize them to enhance website loading speeds. Finally, she stresses the importance of regular monitoring and testing of DNS to avoid potential issues in the future and ensure the smooth operation of websites and web applications.