Legacy architecture was throttling a 150-year-old brand

Helly Hansen has outfitted professionals and enthusiasts since 1877, but its digital storefront wasn't keeping pace with its heritage. Operating across 38 global markets with multiple properties — HellyHansen.com, HHWorkwear.com, and Musto.com — the company found itself constrained by a legacy Adobe Commerce PWA stack that degraded site performance and limited what the team could ship.

An incremental migration to Next.js and Vercel turned things around: Core Web Vitals moved from failing to passing across every metric, a record-breaking Black Friday Cyber Monday delivered 80% year-over-year growth with zero downtime, and the developer team now runs A/B tests at a pace that was previously impossible.

Client-side rendering was the root cause of poor Core Web Vitals

The performance problems traced back to how the old architecture served pages. The Adobe Commerce PWA relied on client-side rendering for personalization and A/B testing, which meant heavy scripts executed on every page load. The result was blocked rendering and severe layout instability.

The numbers painted a grim picture: Core Web Vitals failed across the board, page load times exceeded 4 seconds, and Cumulative Layout Shift spiked above 2.8. For a seasonal outdoor business where Q4 accounts for 55% of annual revenue, these issues directly threatened peak shopping events.

Starting the migration at the checkout

Rather than betting everything on a single high-stakes relaunch, Helly Hansen adopted an incremental migration strategy with Vercel. Working with Vercel's professional services team, they first conducted an architecture review to settle on the right rendering and caching strategy.

Checkout pages — not the homepage — were chosen as the starting point. This isolated the most critical conversion surface while leaving complex marketing attribution systems untouched. Server-side experimentation allowed the team to A/B test different checkout flows in real time. The Vercel CDN kept pages fast for customers in all regions, while Vercel Functions provided automatic scaling during traffic surges.

Core Web Vitals went from red to green in five months

The pivotal shift was moving from client-side to server-side rendering via Vercel's Edge Network, which eliminated the root cause of the slowdowns. Key metrics improved dramatically:

  • Load times fell from over 4 seconds to a consistent 1.8-2 seconds
  • Cumulative Layout Shift was virtually eliminated

By limiting the initial migration to a single part of the customer journey, Helly Hansen could precisely attribute improvements to Next.js. Vercel Web Analytics provided quantifiable data on load times, conversion rates, and Core Web Vitals — evidence strong enough to justify the global rollout, which completed in under six months.

From Black Friday anxiety to record sales

Before the migration, Black Friday meant stressful operations, frequent outages, and maintenance firefighting during the company's most revenue-critical period. The Vercel-powered infrastructure changed that calculus entirely.

Next.js automatically optimized product and pricing data through the Vercel Data Cache, while Incremental Static Regeneration (ISR) and cache shielding kept performance consistent even under peak traffic. When the team spotted third-party scripts slowing the site during Black Friday, they shipped a low-risk fix during the code freeze — a move that wasn't possible on their previous platform.

The results set a new benchmark:

  • 80% year-over-year growth with zero downtime
  • 2x lift in conversion rates, which justified increasing marketing spend mid-campaign three separate times

"Conversion was so high because the site was so fast. During Black Friday, we increased our performance marketing spend three times because it was so profitable."

Anshika Jain, Chief Digital Officer

Breaking out of a one-test-per-month bottleneck

The old platform was also a straitjacket for experimentation, permitting only a single A/B test per month. That made it nearly impossible to optimize the customer experience or react to market shifts.

The migration to Next.js and Vercel established an API-first, server-side rendering foundation that unlocked a full-scale testing program using feature flags. Developer velocity improved markedly: the team deployed Constructor.io for personalization in just 11 weeks and now runs 5-6 A/B tests per sprint, up from one per month.

That increased agility translated directly into business results:

  • 21% ecommerce growth while industry peers remained flat
  • Highly personalized customer experiences at near-zero latency within a year of launch
  • Demonstrated that speed and personalization can coexist without compromise

Lessons from the leadership team

Helly Hansen's CDO, Anshika Jain, offered guidance for other digital and technology leaders facing similar transformations:

  • Prioritize speed as your foundation — faster experiences convert better and unlock personalization, experimentation, and rapid feature delivery. Invest early in infrastructure that guarantees fast, reliable experiences.
  • Test, learn, and scale — don't attempt a sweeping overhaul on day one. Use small, data-driven experiments to prove value, build momentum, and de-risk larger transformations.
  • Embrace change as the norm — change is the new operating system. Organize for agility, expect resistance, and make adaptability muscle memory.

"It's not that you won't fail. It's more about who's in it with you. And it has always felt like that with Vercel. That's the hallmark of a true partnership."

Anshika Jain, Chief Digital Officer

The migration solved Helly Hansen's immediate performance crisis, but the larger outcome is a scalable, future-proof ecommerce foundation that lets the brand keep pace with — and outrun — competitors built on modern stacks.