How Linktree scaled to support 4 million new users in 3 months

You might not be expecting Selena Gomez to join your platform — but serious scaleups prepare for just that kind of traffic spike with tech that empowers visibility, useability, and performance.

Linktree is typical of SaaS startups; a DevOps approach to continuous delivery and improvement drives vendor choice. A small team with big goals for growth, Linktree worked with Fastly to improve their security posture and to scale seamlessly as they faced a 3-month signup spike where millions of new users created an evergreen link to their online content.

A WAF up to the challenge

Using a WAF doesn't automatically mean you've hit the tech jackpot: it should effectively protect applications in production without blocking legitimate traffic, impacting app performance, or creating too many false positives. Linktree initially had another vendor’s WAF but sought out Fastly for a more comprehensive solution.

“We had rules set up in our existing WAF, but it was case by case rather than a holistic solution. We wanted it to cover the whole edge and integrate with our CDN.”
Paul Oram, Engineer Manager

The Fastly team worked with Linktree during the proof of concept (POC) to assess what Fastly next-gen WAF deployment option would be most effective. Fastly’s Cloud WAF deployment option offered a dev-friendly surprise: the accessibility to work at the edge and use Typescript code at the application layer.

“We used it quite heavily right off the bat, to throw ourselves in and see how it reacted, but also to augment our security across attack surfaces. There was a time when I was in the console all day every day, looking at attack surfaces and putting in rules to either block or rate limit them.”
Matt Ogle, Platform Engineer

Scalability that expects the unexpected

Scalability is all about the what if's. What if we have an extraordinary shift in user behaviour? What if we have an opportunity to grow overnight? What if we have a massive unexpected spike in signups that shows no sign of slowing down?

Linktree chose to scale up by moving to Fastly’s edge cloud platform. The switch freed up the Linktree team and let them use much of their existing code.

Two minutes till impact

The Fastly next-gen WAF POC had an immediate impact by augmenting a code fix for specific issues. A bad actor had written a Python script that created multiple fake accounts daily.

Within two minutes of launching the Cloud WAF POC, Linktree detected the Python bot and created new rules to block it. Shutting down fake accounts solved a major headache for the customer success team and helped Linktree validate their user numbers.

When you’re a tech startup with a relatively small team, you need the tech that will amplify your efforts to launch fast and grow faster.

“We’ve got a lot on our plate, so we look for technology that gives us what we need out of the box. [Security solutions like Fastly’s next-gen WAF] that you can turn on and immediately get known threat signature detection is really helpful for a team like ours.”
Matt Ogle, Platform Engineer

Uptime gets an overnight boost

Hot on the heels of that win was a massive performance boost. Uptime was at 96%, and that didn’t bode well for how Linktree would cope with a traffic spike.

After deploying the Fastly CDN, overnight Linktree’s uptime surged to 99.999%, putting the platform in a much better position to prepare for the unexpected.

“Selena Gomez might join the platform, then [Metallica], and that sets off a cascade of new users that you just can’t predict. Having Fastly scale underneath us...has been super beneficial.”
Bradley Shawyer, Head Of Engineering

The moment of truth

With changing consumer behaviours — spending more time on social media and shopping online — Linktree saw steady growth. Then in the first three months of 2021, that growth spiked to add 4 million new users, with signups peaking at around 43,000 per day.

Evolving consumer and market conditions created Linktree’s scaleup moment of truth, and they were ready for it.

The Linktree future with Fastly

For Fastly, working with Linktree was an opportunity to support a highly technical team that loves the WAF's programmability and the freedom to jump into code and customize what they need.