How the Architecture Evolved to 99.999% Availability, 8 Million Visitors Per Day, and 200,000 Requests Per Second

The AOL homepages receive more than 8 million visitors per day.  That’s more daily viewers than Good Morning America or the Today Show on television.  Over a billion page views are served each month. has been a major internet destination since 1996, and still has a strong following of loyal users.

The architecture for is in it’s 5th generation.  It has essentially been rebuilt from scratch 5 times over two decades.  The current architecture was designed 6 years ago.  Pieces have been upgraded and new components have been added along the way, but the overall design remains largely intact.  The code, tools, development and deployment processes are highly tuned over 6 years of continual improvement, making the architecture battle tested and very stable.

The engineering team is made up of developers, testers, and operations and totals around 25 people.  The majority are in Dulles, Virginia with a smaller team in Dublin, Ireland.

In general the technology in use are Java, JavaServer Pages, Tomcat, Apache, CentOS, Git, Jenkins, Selenium, and jQuery.  There are some other technologies which are used outside that stack, but these are the main components.

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