Shipping headless commerce without losing the checkout

Headless commerce is often sold as a clean cut: peel the storefront off the monolith, stand up an API, and watch conversion rise. In practice the catalog, promotions, inventory, and checkout are one nervous system. Cut the wrong nerve and the customer still sees a price that finance cannot honour.

At Orca-Tech we treat a headless move as a series of seams, not a rewrite. The first seam is always the money path. Until cart, tax, and payment contracts are stable, a prettier marketing site is just a faster way to fail at the last step.

Start with the money path

We isolate cart and payment behind explicit APIs: add line, apply promotion, calculate tax, capture. Those four calls become the contract both the old theme and the new storefront must honour. If they stay stable, content and merchandising can move independently.

Most failed programs invert that order. They rebuild the homepage in a new framework, then discover that gift cards, split shipments, and regional VAT were encoded as theme liquid. The demo looked modern. The checkout leaked money.

What we keep on the monolith — for a while

Admin, purchasing, and the warehouse integration can stay put for a quarter. Headless is a storefront strategy, not an ERP replacement. We draw a map of reads versus writes and only move the reads the customer actually sees.

When the money path is green in production for two peak weekends, we move category pages, then search, then account. Each step has a rollback that is a DNS change, not a prayer.