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LaunchDarkly is a feature management platform that helps enterprises deploy new features more quickly while minimizing risk. Feature flagging ensures that their customers deliver the right feature to the right end users at the right time, safely. With a focus on lightning fast performance and delivering consistent user experiences, LaunchDarkly uses Fastly's edge cloud platform to serve 6 trillion feature flags daily, reaching 14 million mobile devices and browsers and 4 million servers worldwide, ensuring their customers with SLAs for performance and uptime.

launchdarkly.com/
Industry: SaaS
Location: Oakland, CA
Customer since: 2014

Favorite features

  • Fastly API
  • Instant Purge
  • Fastly TLS
  • Enterprise Support

LaunchDarkly’s 200-ms kill switch, built on Fastly for scalable control in real-time

Removing speed limits from the software development lifecycle

In fast-paced software development lifecycles, teams have competing needs: speed and security. Speed makes products better and faster while also keeping users happy and engaged. Security ensures deployments don’t break something or send frustrated users to a competitor’s app. Especially in the world of mobile, developers need to keep features rolling out without friction or they risk watching their product slide down the app store rating.

When development teams embed LaunchDarkly’s SDK into their applications, feature management allows them to decouple deploying code from release features, enabling control at a fine-grained level without diminishing speed. Development teams can deploy code whenever they’re ready, and product teams release features when they’re ready, whether that’s to every user, a test group, or a specific user demographic or region. And if disaster strikes, LaunchDarkly, gives customers a 200-millisecond kill switch. Feature flags let anyone turn off a feature instantly without rolling back code, so user experience is protected.








"Fastly’s caching is our gas pedal: our customers and their end users all benefit from caching closer to the edge." Arun Bhalla
Engineering Manager

"With Fastly providing a shield between our web application and the public cloud, we see significant performance benefits." Arun Bhalla
Engineering Manager

Instant purging increases update speeds by 90%

LaunchDarkly chose Fastly for the Instant Purge capability, which immediately stops delivering cached versions of that content and starts serving fresh content as soon as a customer issues a purge request, via either the Fastly control panel or an API call. When LaunchDarkly started in 2014, it took several seconds to propagate updates to a feature flag globally. Now that Fastly is a core part of LaunchDarkly’s infrastructure, when one of their customers changes a feature flag, Fastly’s platform purges any content related to that flag in milliseconds.

By comparison, other CDNs could take several seconds – often minutes – for purge requests to propagate through the global network, which drives up their expenses or causes errors. And some hosting providers even charge for each purge request. By integrating with Fastly’s API, LaunchDarkly issues those purge requests automatically, streamlining that workflow, and shielding them from infrastructure expenses.





“Fastly is fundamental to the service we offer. The fact that Fastly processes that purge in less than a second lets us guarantee that worldwide, we’re not going to serve any stale settings or content.” Arun Bhalla
Engineering Manager

Shielding maintains performance when traffic unexpected surges

LaunchDarkly also uses Fastly's shielding with request collapsing for faster page loads and better overall performance. Before fresh content is cached, all requests for it normally go to the origin, which can drain computing resources and degrade performance. When requests surge, this can cause performance challenges. By using request collapsing, Fastly’s platform consolidates all cache miss requests into a single request, holding them in a queue. Fastly’s edge cloud platform then makes a single consolidated request for the content and serves queued requests with the cached content, protecting the origin from a barrage of server requests.





“Our cache hit ratio with Fastly is very high. Every hit to Fastly’s edge cloud platform is saving our backend services from having to do more work—and then reducing the response time for the end user as well as the cost.” Arun Bhalla
Engineering Manager

Continuing a trend of exponential growth

LaunchDarkly had a chance to test the value of Fastly’s shielding in 2019, when their customer was launching a hotly anticipated online game. Expecting a stampede of gamers, the company integrated LaunchDarkly into their sign-up page—something LaunchDarkly didn’t know about until traffic started to surge. Suddenly 50,000 requests per second were passing through Fastly, a peak that lasted several hours. They were reaching totally unexpected traffic equivalent to 150 million monthly active users for one account, on top of their usual traffic.




“Fastly shielded a load of over 50K requests per second, during a peak that lasted several hours, which made the difference in our ability to handle our customers’ traffic during a launch. We would have not been able to handle that surge without Fastly.” Arun Bhalla
Engineering Manager

Since the beginning of their partnership with Fastly, LaunchDarkly has grown exponentially: serving 4 billion feature flags daily in 2016, to 400 billion feature flags daily in 2019, and looking at trillions of feature flags in 2020. As their business has evolved, they’ve also migrated customers to use TLS 1.2. Using Fastly logs helps accelerate that process. “Using Fastly's real-time streaming logs, it’s really easy for us to figure out which customers we need to contact and ask them to upgrade their software,” Bhalla said. “It’s worth pointing out that with some of our other request logs, it’s much harder to do that sort of thing.”

“Our key performance metrics are the time for our SDKs to serve flags to customers’ end users and flag update time. Fastly is absolutely crucial to both of those metrics.” Arun Bhalla
Engineering Manager

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