Our guest post today comes from Olivier Devaux, co-founder of feedly, a reading app founded in 2008 in Palo Alto. feedly offers a free version as well as a Pro version that includes power search and integrations with other popular applications, including Evernote, LinkedIn and Hootsuite.

With over 15 million users, feedly is one of the most popular apps for purposeful reading in the world. People can tailor their feedly accounts to serve up their favorite collection of blogs, web sites, magazines, journals and more. Our goal is to deliver to readers the content that matters to them. Over the past year, we have focused on making feedly the reading app of choice for professionals.

For our first few years, we had around four million users, and we hosted all of the content we aggregated on our own servers. We ran a small instance of Google App Engine to extract picture URLs within articles.

In the middle of last year, our servers were overwhelmed with hundreds of thousands of new signups, and we experienced our first service outage. The first thing we did was move all of our static content to App Engine. Within an hour we were up and running again with 10 times the capacity we had before. This turned out to be a good thing – we added millions more users over the next few months and more than doubled in size.

It’s been almost a year since that day, and we’ve greatly expanded our service with Google Cloud Platform. We now use App Engine as a dynamic content delivery network (CDN) for all static content in feedly, as well as to serve formatted images displayed in the app or desktop.

A fast response time is even more important on mobile, and App Engine helps us load images immediately so that there’s no lag when users scroll through their feeds. As a feedly user scrolls through content, the app sends App Engine information in the background about what articles are coming next. App Engine then fetches images from the article page on the Web, determines the best image, stores it in Cloud Storage and receives a serving URL from the Image service. For users, this leads to a seamless scrolling experience.

To optimize the feedly user experience, we make heavy use of the Memcache API and App Engine Modules and the Taskqueue API. The combined result of these services allows us to cut our response time for user requests in the app down to milliseconds.

As an engineer, one of my favorite things about App Engine is that it generates detailed usage reports so we can see the exact cost of our code, like CPU usage or the amount we’ve spent to date, and continue to optimize our performance.

We learned the hard way what happens when you don’t prepare for the unexpected. But this turned out to be a blessing in disguise, because it prompted us to move to Cloud Platform, and expand and improve our service. App Engine has taken pressure off our small team and allowed us to focus on building the best reading experience for our users. With Google’s infrastructure on the backend, today we only need to worry about pushing code.

- Posted by Olivier Devaux, co-founder of feedly