Why speed matters?
Before we start I just want to point out several really important reasons why speed matters.
First of all, it affects the readers, users and buyers on your website. People don't like standing in queues and wait for something to happen. The same reflects when opening a website, they just get frustrated if it takes more than a couple of seconds. The graph below shows how speed affects conversions.
Image source: KISSmetrics: How Loading Time Affects Your Bottom Line
If an e-commerce site is making $100,000 per day, a 1 second page delay could potentially cost you $2.5 million in lost sales every year.
... makes you think twice, doesn't it?
How to test website performance?
You cannot start optimizing a website before you know what to optimize. So, I'll show a few tools that everybody can use to test the speed of their site. There are many tools, but I'll show my top 3 favorites. For the example test I'll use Webiny's blog page (http://www.webiny.com/blog/).
All that is then taken into account and a performance grade is evaluated. One cool thing about Pingdom is that it can then compare the speed of your website to other tested websites in the world.
As you can see Webiny scored 97/100 performance grade and the resulting speed test says that the website is faster than 97% of all tested websites.
Below the speed test results you'll find several tabs with details about your website, some even come with an explanation what you can do to improve your score.
YSlow & PageSpeed Insights
These two tools are quite similar. YSlow is developed by Yahoo, and PageSpeed Insights by Google. They both work similar like Pingdom, but they have some better insights and come as a Firebug plugin for Firefox (link) or Developer tools plugin for Chrome (link).
Firebug - YSlow
Google Page Insights
You can see that websites that run on Webiny are optimized to the smallest detail when it comes to performance grades and page speed load time. It doesn't matter if you use a Webiny free theme, or if you make your own, the performance will always be very satisfying to you and your users.
A website might perform very good on a smaller number of visitors, but what happens when some major blog, or news portal places a link in some article to your website and you get 10.000 visitors in one hour?
The test was conducted using ApacheBenchmark tool with 500 requests and 20 concurrences. (ap -n 500 -c 20). Note that the test was issued from a different server that's not in the local network.
Latency & CDN
Latency is a measure of time delay experienced in a system, the precise definition of which depends on the system and the time being measured.
In simple terms, (network) latency is a time delay which tells us how much time is needed from the point when we ask for a domain/URL in our browser, until the moment when we get a reply from the server. So, the lower the latency is, the better.
Have a look at this video for a in-depth explanation what, and how, does a CDN work.
Webiny will offer CDN as a part of its paid packages in the near future. You'll get top notch performance, that usually cost several thousands of dollars and are only available to exclusive clients, for just a couple of dollars a month.