Case study — Merchbay
Replatforming a 40-country retailer without missing a Black Friday
A headless storefront migration executed market by market — ending with a Black Friday that ran 22x normal traffic at 0.9-second page loads and zero incidents.
Industry
Retail & E-Commerce
Duration
9 months
Team
8 people
Services
Web Development, Cloud Solutions, Quality Assurance
The challenge
Merchbay's monolithic commerce platform had become a business constraint wearing a technology costume: 6-second mobile page loads in key markets, a 40-minute full-site deploy that froze releases for days before every promotion, and a Black Friday the previous year that spent 90 minutes in degraded checkout — an outage the finance team could price precisely at €1.8M.
The board approved a replatform with one non-negotiable: the migration could not put the next Black Friday at risk. That gave us nine months and no appetite for a big-bang cutover.
How we approached it
We rebuilt the storefront headless — Next.js at the edge over the existing commerce backend via a GraphQL federation layer — so the risky backend migration could be deferred entirely. Market by market, traffic shifted behind a routing layer: New Zealand first as the low-stakes proof, then progressively larger markets as monitoring confirmed each wave.
Performance was engineered as a budget, not an aspiration: 200KB JavaScript ceiling per page type, image pipelines with AVIF and responsive sizing, and product pages statically regenerated on inventory events rather than rendered per-request. CI failed any pull request that broke the budget.
For peak readiness we load-tested at three times the previous year's peak using replayed production traffic shapes — which surfaced a checkout inventory lock contention issue two months before it would have surfaced itself on the year's biggest revenue day.
Outcomes
The results, as measured
0.9s
median LCP globally, down from 6 seconds on mobile
22x
Black Friday traffic peak handled with zero incidents
+28%
conversion rate lift measured across migrated markets
40min → 4min
deploy time, unlocking daily releases
“Last year Black Friday was a war room with pizza and dread. This year the biggest incident was someone's espresso machine. Same traffic. More revenue.”
Ingrid Sørensen
VP of Digital, Merchbay
Built with
- Next.js
- TypeScript
- GraphQL
- Redis
- Vercel
- Algolia
- k6
- Datadog
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