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Pandora: Capacity Has Grown 50x in Eight Years
Pandora CIO Steve Ginsberg shared some of Pandora's network and delivery secrets at the Content Delivery Summit in New York

As CIO for Pandora, Steve Ginsberg has helped the music service increase capacity by more than 50 times in the eight years he’s been with the company. "When I arrived in 2006, we had grown to over two million users," he told the audience at the Content Delivery Summit today in New York. "We had consumer switches with no manageability. We actually moved out of a data center because they couldn’t give us the additional bandwidth we needed."

Ginsberg spent the first part of his presentation talking about the company’s history, starting with the Music Genome project on which the company's personalized radio service is based. But the real focus of his talk was on how Pandora delivers music to more than 250 million users.

"We used just-in-time scaling," said Ginsberg. "Pandora was mostly used at work back then, and Thursday was the busiest day of the week.

"The original architecture was built around 1Gbps links, which is what we could get from ISPs," he said. "We were turning up a new 1Gbps link per month."

Ginsberg said the company scaled to 16 one-gigabit links, but needed to do more in terms of the servers.

Pandora made a move from Network Address Translation (NAT) to Direct Server Returns (DSR) as a way to move from server pairs—the redundant 1Gbps links, mentioned above, were always implemented in pairs—to server pools.

Ginsberg said that popularity of the Android and iOS platforms represented a sea change for the company.

"In 2007, we saw the wave of smartphones," said Ginsberg. "Pandora was the number one app on the iPhone and that was a game changer for us."

To meet demand for different types of smartphones, Pandor increased the number of supported audio formats from one to fourteen.

Mobile delivery of Pandora content, which was growing exponentially, led the company to move towards a CDN-style delivery. Ginsberg noted that code that runs at night tells the servers which content was the most popular over the past day.

"We could have used an external CDN, but so far we’ve chosen not to," said Ginsberg.

Based in California, the company has run failover scenarios where they don’t just lose a data center but lose an entire coast.

In addition, Ginsberg says that border gateway protocol routing helps the company with its routing models, and the company monitors servers, network traffic patterns, and a number of other analytics tools.

Today all production media is dual stack, available through all transit and peering.

Ginsberg notes that Pandora's 250 million registered users make the company the third-largest advertising network after Google and Pandora. "We provide over 1.8 billion listener hours per month," he said, over half of which happen in cars.

Even with this high number, however, it only represents 10% of all radio listening. And that’s the path for growth for Pandora.

"Our ambition is to deliver music globally, with a global marketplace that connects fans, artists, and listeners everywhere."