Can excess web traffic on a webpage slow down the portal or even result in page not opening?
Most definetly YES. It is the way a Denial Of Service attack works. The hacker sends so many messages/requests for answer that the site is brought to a standstill, or worse, the server crashes.
Does it happen during holiday time to online shopping pages?
yes but also depends on their server, Internal and external factors
8 Reasons Your Website Is Slow
Common causes of a slow website
Since a few days amazon.in is not opening fully and very slow. What can cause the error
Even it's app has become very slow
But other portals at same time are opening properly
you can try ipconfig /flushdns, just open cmd with administrative rights, also reset router.
Is amazon.in slow on other pc and other web navigators?
the thing is that Amazon pings will always timeout, they filter ICMP (Internet Control Message Protocol) one reason is Denial of service attacks based on ICMP (Denial of Service (DoS)), so when you ping amazon.in you get lost=4 (100%)
try to see if this test will work
The short answer is yes. When many users are trying to access a site, it can be slowed down significantly. A good example is when a small website or service is featured on a tech website and tons of people flock to it, slamming it and slowing it down.
This happens at my college; when it's time to schedule classes and everyone is online trying to do so at the same time, it slows to a crawl as if you're on dial-up.
How do portals which slow down due to excessive users online deal with the speed for users? Amazon.in is not opening since few days