E-commerce Checkout & Payments Platform

Challenge

A European direct-to-consumer e-commerce operator running many brands and landing-page funnels had a separate checkout and payment integration for each one. Every new brand or payment method meant another bespoke build, and order data was scattered across shops, payment dashboards and marketing tools.

Solution

We designed and built a single multi-tenant backend, exposed as a REST API, that every brand's funnel plugs into. It owns the checkout session, pricing with tax and shipping, the order lifecycle and one-click post-purchase upsells. Payments are provider-agnostic: Stripe, PayPal, Klarna and Dalenys (including 3-D Secure) are configured per tenant and switched without code changes. Incoming webhooks from providers and shops are reconciled to orders, and a transactional outbox with a background processor guarantees that order events reach Shopify, Klaviyo and ad-tracking attribution exactly once. Multi-currency support with scheduled exchange-rate updates rounds out the platform.

Stack: PHP 8.3 with the Slim framework in a domain-driven layered architecture, MariaDB, PHPUnit, PHPStan, Docker and CI pipelines with load tests.

Result

One platform now powers checkouts across all of the client's brands. Adding a brand or a payment provider is a configuration task rather than a project, and the client's own team keeps extending a tested codebase we handed over with full documentation. Client name withheld under NDA.