So, Fastly Inc. (FSLY) is having a moment. A big one. The stock is up a staggering 145% over the past month, and it was still climbing on Monday afternoon. The wild part? There wasn't any new company-specific news driving the action that day. Traders appear to be simply continuing their love affair with the stock following a knockout earnings report last month. Let's unpack what's really going on.

The Engine Behind the Rally: Earnings and the AI Story

Last month, Fastly reported its fourth-quarter numbers, and they were good. Really good. The company posted record revenue of $172.6 million, a 23% jump from the same period last year. Security revenue did even better, climbing 32%. Perhaps more importantly, Fastly reported a non-GAAP operating income of $21.2 million, a welcome shift from a loss in the prior year. They also gave investors a glimpse of the future, guiding for full-year 2026 revenue between $700 million and $720 million.

But the numbers are only part of the story. The narrative that's really got investors excited is about artificial intelligence. Management explicitly said AI is becoming an increasing tailwind for the business. The logic is straightforward: as more internet traffic becomes automated and AI-driven, the demand for tools to manage that traffic—which is Fastly's bread and butter—grows. CEO Kip Compton has been talking up the company's transformation and improved growth profile, and the market is listening. That earnings report lit the fuse for this sharp rally, and Monday's move suggests the momentum hasn't fizzled out yet.

The Short Squeeze Accelerant

Here's where it gets spicy. Fastly has a sizable amount of short interest—investors betting the stock will go down. Based on available market data, about 17.09 million shares were sold short, representing roughly 12% of the float. That's not an insignificant number.

Now, when a stock with high short interest starts to rise sharply, it can create a feedback loop. As the price climbs, the short sellers start losing money. To limit their losses, they often have to buy back the shares they borrowed and sold—an action called "covering." This buying pressure can push the price even higher, forcing more shorts to cover, and so on. With Fastly trading near the upper end of its 52-week range, this elevated bearish positioning is almost certainly adding fuel to the fire and amplifying the upside moves. It's a classic short squeeze in the making.

Technical Strength Confirms the Bullish Run

Looking at the chart tells a clear story of powerful momentum. Fastly shares have staged an incredible comeback, surging from lows around $5 to above $20. On Monday, the stock was pushing near its recent high of $21.27. More tellingly, the stock is trading well above its 20-day, 50-day, and 200-day moving averages. For the technically inclined, this is a strong bullish signal across short-, medium-, and long-term timeframes. It reinforces the idea that the rally fueled by AI optimism and strong earnings is holding strong, even on a day without fresh news.

Market data shows Fastly with an exceptionally high Momentum score, and the price trend is bullish across all measured periods.

Where Things Stand Now

So, where does this leave us? Fastly shares were up another 7.65% at $21.67 on Monday. The stock is now knocking on the door of its 52-week high of $21.85. It's a remarkable run that blends solid fundamental progress—record revenue, a path to profitability, a compelling AI narrative—with the kind of market mechanics (hello, short squeeze) that can turn a good rally into a spectacular one. Investors are betting that the AI tailwind is real and that Fastly is well-positioned to ride it. For now, the momentum is firmly on their side.