Jonatan Witoszek

Adyen payment app for Saleor's app-based architecture

• Evolved the Adyen app from an early prototype into a production-grade integration for key merchants. Engineered support for complex provider workflows, including 3D Secure, split payments, Apple Pay, stored payment methods, captures, refunds, and cancellations.
• Improved the reliability of event-driven payment flows in a multi-tenant serverless environment. Introduced reconciliation logic, idempotency safeguards, and DynamoDB-backed storage to manage tenant configuration, transaction state, and expiring operational logs.
• Built out advanced observability and distributed tracing across Saleor, the app, and the Adyen API using custom OpenTelemetry infrastructure. This directly accelerated the investigation of webhook bottlenecks, retries, p99 outliers, and merchant-specific production issues.
• Established architectural patterns that were later adopted across other integrations, including DynamoDB usage, observability setups, typed webhook schemas, and integration testing workflows.

SPA admin panel for Saleor-powered stores

• Led rollout of Saleor's new Transaction API experience in the Dashboard, including split payments, payment balance views, refund approval and execution workflows, manual capture, and feature-flagged migration from the legacy payments model.
• Re-architected filtering in a large React/TypeScript SPA into reusable abstractions, improving reliability and consistency across Products, Orders, Customers, and modal workflows.
• Improved engineering workflows in the Dashboard through AI-assisted development guardrails and large-scale codebase maintenance, including deterministic Claude Code hooks and dead-code cleanup across 900+ files.
• Led the migration to Saleor's unified Extensions experience, consolidating apps, plugins, and webhooks under /extensions with backward-compatible routing, onboarding updates, and GA rollout.

TypeScript SDK for building Saleor apps across frameworks and runtimes

• Rewrote App SDK from a Next.js-centric library into a universal, platform-agnostic toolkit by introducing reusable runtime abstractions and removing legacy middleware.
• Added first-class support for Web API runtimes (Cloudflare, Deno, etc.) and AWS Lambda, enabling Saleor apps to run outside Vercel in serverless and edge environments.
• Built working examples for AWS Lambda, Cloudflare Workers with Hono, and Deno Deploy with Hono, making the SDK easier to adopt across serverless and edge platforms.

Monitoring infrastructure and authentication experience

• Migrated Datadog dashboards and alerts to Terraform, moving monitoring into version-controlled infrastructure as code.
• Improved operational reliability by auditing monitors, reducing alert noise, and strengthening logging around app installation and production issues.
• Modernized the Saleor Cloud identity experience by replacing legacy Keycloak templates with a React-based theme built with Keycloakify and the Macaw design system.

Templates, linting, and developer tooling for Saleor apps

• Helped create Saleor's payment app template, establishing configuration, validation, and testing patterns reused across future payment integrations.
• Built reusable ESLint tooling for Saleor apps, including a recommended config and custom validation rules that improved consistency across integrations.

Saleor's design system and component library

• Expanded Saleor's design system with reusable components such as Chip, Avatar, Tooltip, and Pill, improving UI consistency across multiple products.
• Introduced framework-agnostic navigation patterns for shared components like IconButton, Backlink, Sidebar, and Pagination, enabling custom Link integrations and better power-user workflows such as opening views in new tabs.
• Modernized the library for newer React patterns by fixing Strict Mode and React 18 compatibility issues and improving Storybook-based development workflows.