Case file
Priority
MSN.002
Cartographer
A headless commerce API powering three storefronts from one catalogue — carts, inventory, and payments behind a clean JSON contract.
The brief
Three brands, three storefronts, one warehouse — and three separate codebases duplicating cart logic, each with its own bugs. The mandate: one API to rule the catalogue, flexible enough that each brand could keep its own front-end identity.
The build
- Resource-oriented API with cursor pagination, sparse fieldsets, and aggressive HTTP caching (
ETag+stale-while-revalidate). - Inventory reservations with pessimistic locking scoped to checkout sessions — no more overselling flash-sale stock.
- Stripe integration behind a payment abstraction, so a second provider can be added without touching checkout flows.
- Contract-first development: OpenAPI spec is the source of truth, CI fails if implementation drifts.
Transmission log
- Cart bug reports across the three brands: -71% in the first quarter.
- New storefront integration time: six weeks → four days.
- Black Friday peak handled at 9× normal traffic with p95 under 120ms.
Debrief
Need results like this on your project?
Same process, your problem: scope it honestly, build it fast, debrief with numbers.