How Carve Designs Turned a 55%+ TTFB Speed gain Into a 12.8X ROI on Nostra

Carve Designs is a coastal women's swim and active apparel brand. Their customer shops on her phone, often mid-scroll, often mid-thought, often deciding in seconds whether a swim top, a tank, or a cover-up is worth the click. The traffic mix reflects it. The bulk of Carve Designs' sessions come from mobile, which is also where every fraction of a second matters most.

Apparel, and swimwear in particular, is unusually sensitive to trust cues. Shoppers are spending real money on items they can't try on, often during paid-social moments. Latency on a product page reads as friction, hesitation, doubt. Latency on a cart drawer can lose the order entirely. The category dynamics make Carve Designs exactly the kind of brand where edge-level speed gains translate directly into conversion outcomes.

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Carve Designs ran Nostra against a live production holdout of a 50/50 traffic split. A statistically significant segment of shoppers continued to receive the original, unaccelerated experience, while the rest were served the Nostra-accelerated version. Same site, same products, same campaigns, same promotions. The only variable was speed.

That speed showed up first at the network layer. Nostra cut Time to First Byte by more than 55% on Carve Designs' top 10 most-trafficked URLs. The homepage, the sale landing pages, the new arrivals collection, and every other high-volume entry point loaded materially faster on the Nostra side of the test. TTFB is the foundation everything else sits on. Faster TTFB means faster paint, faster interaction, faster product image, faster add-to-cart. Move TTFB and you move the whole experience.

The test ran across more than 317k sessions, spanning peak shopping moments, paid and organic traffic, new shoppers and returning customers. It was a real-traffic A/B test, measured the same way every result Nostra publishes is measured.

The faster TTFB worked its way down the funnel. Most of the impact came from mobile, and that's where the story sharpens. On mobile traffic, Carve Designs saw a conversion rate lift of 6.03%. CVR moved from 2.37% on the control side to 2.52% on the Nostra side. Revenue per visitor on mobile lifted 5.76%, climbing from $4.45 to $4.70. That's 26 cents of additional revenue per mobile shopper, compounded across hundreds of thousands of mobile sessions over the course of the test.

Blended across the full audience, the picture stayed strong. Overall CVR lifted around 4%. AOV lifted 1%. Revenue per visitor, blended across mobile and desktop, lifted 4.66%, or roughly 21 cents per shopper. Three numbers, all moving in the same direction, all flowing from the same upstream change at the network layer. By the time the math rolled up, Nostra was returning 12.8X on every dollar Carve Designs spent on it.

Nostra doesn't make money unless the customer does. The 12.8X ROI is calculated on top of a pricing model that only invoices when Nostra is driving incremental revenue against a live holdout. There is no version of this case study where the math doesn't work, because if it didn't, there wouldn't be an invoice in the first place.