Shares of personalized online apparel company Stitch Fix (NASDAQ:SFIX) skyrocketed on Tuesday. The stock jumped an impressive 39% to a new all-time high. Year to date, shares have now nearly doubled.

Investors have applauded the company's resilience during a pandemic this year. In addition, the company's just-posted fiscal first-quarter results -- the reason for the stock's big gain on Tuesday -- highlighted accelerated growth in active clients and a promising outlook from management.

Here's a closer look at some of the most encouraging metrics from management's business update this week.

A Stitch Fix box on a doorstep

Image source: Stitch Fix.

1. Double-digit revenue growth

Stitch Fix's revenue for its first quarter of fiscal 2021 increased 10% year over year to $490.4 million, beating analysts' average forecast for revenue of $481 million. This led to earnings per share of $0.09 -- soaring past a analysts' forecast for a loss per share of $0.20. 

2. Record levels of client additions

The company added 241,000 new clients during the quarter, bringing total clients to 3.8 million. This marked the company's highest-ever sequential client additions. Further, active client growth accelerated during the quarter on a year-over-year basis. Active clients were up 10% year over year. This compares to 9% growth in the fourth quarter of fiscal Q4.

More importantly, management indicated in the company's fiscal first-quarter earnings call that it expected active client growth to continue accelerating in the coming quarters.

Strong revenue guidance

For the full year of fiscal 2021, management said it expects total revenue to increase at a rate between 20% to 25%, implying that the worst of the impact from the pandemic may be behind the company.

"Our powerful personalization engine is evolving, and innovations in our Fix and direct buy offerings will expand our addressable market, deepen client engagement and grow wallet share over time," said Stitch Fix CEO Katrina Lake in the company's fiscal first-quarter update.

To pull this off, the company will need extremely strong growth in the second half of the fiscal year. Specifically, management expects revenue growth rates to accelerate to levels between 29% and 40% in the second half of fiscal 2021.

While all of this is encouraging, management did warn that its guidance implies that StitchFix doesn't face any "significant disruption from potential government-related COVID mandates."

Of course, since the company doesn't operate any storefronts, the company's business model is likely to be more resilient than traditional apparel retailers if the pandemic does get worse. But there's always a risk that Stitch Fix's fulfillment centers face unexpected challenges.

While Stitch Fix's fiscal first quarter was solid, investors are likely most excited about the company's momentum and management's guidance for strong revenue growth acceleration in the coming quarters -- particularly in the second half of the year.

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