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Why Use a CDN

The web today is a media-rich experience, packed with images, video and other forms of media. These account for most of the network traffic being generated when you navigate through any given modern website. Today's web is also very dynamic and focused on aesthetics, so a good part of the remaining traffic is JavaScript code and CSS stylesheets. The web browser may need to download a few megabytes of files over dozens, perhaps hundreds, of HTTP requests to render a single page.


This makes per-request performance a very important aspect of the overall user experience. But any time spent optimizing the response time for assets means less time spent optimizing the bits that make your site unique. This is where a CDN comes into play, to make asset delivery somebody else's problem, both in response time optimization and in capacity allocation. The origin website focuses on producing content while offloading the part which is cacheable to the CDN. This usually represents the bulk of traffic and often includes some types dynamically-generated content besides purely static files.


A CDN may work in a different number of ways. Stratus in particular works as an architecturally and geographically distributed reverse proxy cache pulling files from your site over HTTP when first requested by a user's browser. Once cached at one of our locations, files are served as many times as needed to any user that requests them.


To ensure fast delivery of content, Stratus is designed to handle much more concurrent user connections, requests and network transfer rates than a typical website can, be it over HTTP or HTTPS. This is the core of what it provides, but you also get protection from request surges and content-control features. We'll take a more detailed, and technical, look into them in later posts.


Stratus is a content delivery platform developed at SAPO and is being used by its main services since July 2014. SAPO's homepage, the leading news portal in Portugal, with over 1 million daily pageviews, was one of our first clients. We improved their page load time by serving more than 65 million of their news images per day. SAPO Mail, with more than 6 million pageviews per day, is also using Stratus to offload assets with excellent results (a 99.8% decrease in requests).

Our main goal is to serve content faster and in the most flexible way, with a special focus in Portugal and Portuguese-speaking countries (particularly in Africa), where our main clients need to  accelerate their websites and applications. We built a powerful caching engine and tied it together with advanced distributed systems and security measures.

Two years since our first deployment and one year since our first major client, we are happy to deliver the CDN of our dreams: fast, flexible and secure. One you can use to build a modern application.

The Stratus team is a group of young people mad over ideas and obsessed about performance. They go out of their way to raise the bar in what you would expect from a CDN and we could not be happier.

Please feel free to use the comments section to let us know what you would want to hear from us next.

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