The high cost of hidden flaws in luxury online retail - replatforming risks

What happens when high-end eCommerce meets high traffic—and hidden API flaws?

A luxury goods retailer came to thinkTRIBE after replatforming to a composable storefront. With high-value products and even higher customer expectations, any glitches in the customer experience can have a major impact—not just on revenue, but on brand reputation. Their goal? Understand how the new platform would hold up under real-world pressure and peak traffic.

Their initial concerns were around page speed and performance—fears that proved unfounded. But what we uncovered wasn’t a classic site crash. It was more subtle. And just as damaging.

Failing promo codes—Early, and often

Early on during our real-world Load Testing process — well before peak load—promo codes began to fail. 28% of promo code attempts failed outright, returning a misleading “promo code not valid” message.

We’re not talking about page errors or a dramatic crash. Pages loaded. Journeys flowed. Everything looked fine on the surface. To customers, it would have looked like they’d entered the wrong code. They hadn’t. But behind the scenes, something was breaking.

The API wasn’t validating promo codes correctly.

As traffic climbed to peak levels, the failure rate rose with it—reaching a significant 70% failure rate.

That’s seven out of ten customers being prevented from redeeming offers during a key conversion moment—not because the codes were wrong, but because the APIs couldn’t cope.

“Add to Bag” – Or not

As traffic reached peak, another revenue-critical failure appeared: the "Add to Bag" action stopped working properly.

Again, no crash. No obvious red flag. But 30% of attempted adds to bag failed to complete the action. That’s a 30% loss in potential orders, a significant amount of lost revenue in a luxury retail environment.

When real users meet real frustration

The root cause? Struggling APIs

Unlike a more common peak traffic server failure, where it’s clear there’s a problem, this was more subtle. The storefront appeared to be functioning, but core eCommerce functionality quietly crumbled under pressure—taking revenue with it. If left undiscovered, the result? No alarms. No clear signs. Just confused customers and shrinking conversion rates.

The registered user redirect loop

There was also a known issue the retailer needed help quantifying.

Registered users who returned to a previously abandoned basket and logged in during checkout were redirected back to the basket rather than moving to checkout—after entering their delivery details.

It would be confusing. Frustrating. And likely a drop-off point for high-value returning customers. We were able to simulate, quantify, and pinpoint the issue during testing, giving the retailer clear evidence and actionable data.

The CX Takeaway: The risks of overlooking real-world Load Testing

This wasn’t a story of clear failure—the site didn’t crash in a blaze of HTTP 500 errors. It was a case of quiet, compounding losses: a site that looked like it was working, while silently hindering conversions for a significant proportion of customers.

These kinds of subtle, inconsistent failures are typical of struggling APIs— missed by traditional performance or load testing tools. Without real-world Load Testing of actual user journeys they would remain hidden beneath the surface. This is especially important when it comes to composable architectures, which are heavily reliant on APIs.

When your products are high-value, and your customers expect seamless journeys, even small issues can mean big losses. This test bench tale is a reminder that not all CX issues are visible. Some are hidden—until you test like a real user.

Further Resources

Read our top tips for overcoming platform migration risks and maintaining seamless digital CX and performance throughout your replatforming project.

DOWNLOAD GUIDE

Discover how our managed CX and performance services can help you to ensure successful platform migration.