Shopify BigCommerce Senior Developer

Job Description Do you have a desire to build enterprise commerce platforms that power some of the world's most recognized brands? Can you architect headless storefronts on Shopify Plus and BigCommerce Enterprise that are fast, secure, and built to scale? Are you excited to use AI-assisted development tools to write better code, faster, without ever losing sight of engineering ownership and quality? Do you thrive on solving complex B2B commerce challenges — pricing, quoting, procurement, and system integrations — for global clients? If you answered yes, then we want to talk to you! We're looking for a Senior Developer to design, build, and optimize enterprise-grade commerce experiences on Shopify Plus and BigCommerce Enterprise, with a strong emphasis on headless and composable architecture. This role sits at the intersection of deep platform expertise and modern engineering practice — you'll work across the Shopify and BigCommerce ecosystems, contribute to next-generation storefronts built on Hydrogen, Catalyst, Next.js, and React, and bring AI-assisted development into your daily workflow to accelerate delivery without compromising on architecture, security, or code quality. Your platform depth, consulting instincts, and comfort operating at the leading edge of commerce engineering will ensure our clients get resilient, high-performing solutions and a genuine technology partner. You'll collaborate closely with architects, designers, and client stakeholders throughout the project lifecycle, and you'll help shape the reusable accelerators, prompts, and best practices that raise the bar for the whole delivery team. Responsibilities Top 5 responsibilities: - Design, develop, and implement enterprise-grade eCommerce solutions on Shopify Plus and BigCommerce Enterprise, including B2B commerce capabilities and third-party integrations. - Leverage AI-assisted development tools (Claude, GitHub Copilot, Codex, Cursor, or equivalent) for solution exploration, code generation, debugging, unit testing, documentation, and code refactoring, always reviewing and validating AI-generated output for security, scalability, and maintainability. - Architect and build headless and composable commerce storefronts using Shopify Hydrogen, BigCommerce Catalyst, Next.js, and React, applying server-side rendering (SSR), static site generation (SSG), and incremental static regeneration (ISR) as appropriate. - Contribute to reusable AI prompts, engineering accelerators, and coding best practices that improve delivery quality and consistency across the team. - Partner directly with clients to translate business requirements into scalable, secure, and performant technical solutions, providing hands-on consulting and technical leadership throughout the engagement. Additional Responsibilities: - Build and extend Shopify Functions, Checkout UI Extensions, Customer Account Extensions, Shopify Flow automations, Metaobjects, and Shopify Markets configurations. - Develop against the Shopify Admin API, Storefront API, and GraphQL, as well as BigCommerce Stencil, Checkout SDK, GraphQL Storefront API, B2B Edition, REST APIs, and Webhooks. - Implement enterprise B2B commerce features such as account hierarchies, customer-specific pricing, approval workflows, quoting, procurement, and ERP/CRM/PIM integrations. - Build modern engineering solutions using JavaScript/TypeScript, Node.js, React, Next.js, GraphQL, REST APIs, serverless functions, edge functions, and event-driven integrations. - Optimize storefront performance against Core Web Vitals and Lighthouse benchmarks through CDN strategy, caching, image optimization, lazy loading, and performance profiling. - Apply secure coding practices aligned to the OWASP Top 10, including OAuth, JWT, PCI awareness, and secret management. - Build and maintain CI/CD pipelines using GitHub Actions, Azure DevOps, Jenkins, and Docker, including Netlify/Vercel deployment workflows and release management. - Uphold code quality through unit and integration testing, static code analysis (SonarQube, ESLint), code reviews, root cause analysis, and observability/monitoring practices. - Collaborate with architects, QA, and client stakeholders across the full project lifecycle. - Mentor junior developers and contribute to internal knowledge sharing and engineering best practices. Qualifications Top 5 qualifications: - 5+ years of software development experience with mandatory production experience in both Shopify Plus and BigCommerce Enterprise. - Strong expertise in JavaScript/TypeScript, Node.js, React/Next.js, GraphQL, REST APIs, and Headless Commerce. - Proven experience implementing enterprise B2B commerce solutions, including account hierarchies, customer-specific pricing, approval workflows, quoting, procurement, and ERP/CRM/PIM integrations. - Hands-on experience leveraging AI-assisted development tools (Claude, GitHub Copilot, Codex, Cursor, or equivalent) to improve engineering productivity while maintaining high standards of architecture, security, and code quality. - Strong consulting, debugging, performance optimization, communication, and client-facing skills. Additional Qualifications: - Experience with Shopify Functions, Checkout UI Extensions, Customer Account Extensions, Shopify Flow, Metaobjects, Shopify Markets, Admin API, Storefront API, and GraphQL. - Experience with BigCommerce Catalyst, Stencil, Checkout SDK, GraphQL Storefront API, B2B Edition, REST APIs, and Webhooks. - Working knowledge of composable commerce architecture, including Shopify Hydrogen and BigCommerce Catalyst, and SSR/SSG/ISR rendering strategies. - Familiarity with serverless and edge functions and event-driven integration patterns. - Experience optimizing for Core Web Vitals and Lighthouse scores through CDN strategy, caching, image optimization, lazy loading, and performance profiling. - Knowledge of secure API development, OWASP Top 10, OAuth, JWT, PCI awareness, and secret management. - Hands-on experience with GitHub Actions, Azure DevOps, Jenkins, Docker, and Netlify/Vercel deployment pipelines. - Experience with unit/integration testing, static code analysis (SonarQube, ESLint), code reviews, and observability/monitoring tools. - Experience with commercetools, Adobe Commerce, Salesforce Commerce Cloud, Mirakl Marketplace, or Marketplacer a plus. - Familiarity with MCP (Model Context Protocol) and AI Agents a plus. - Experience with Playwright, Cypress, or Storybook a plus. - Understanding of accessibility standards (WCAG) a plus. - Bachelor's degree in Computer Science, Engineering, or a related field, or equivalent practical experience. What We Can Offer You - A career with thought leaders who literally wrote the book on Marketplace Best Practices. - A career in the fast-paced world of retail eCommerce, digital marketplaces, and platform businesses. - A career with first movers who are deploying new business models and strategies worldwide. - A career in a flat management structure without a rigid hierarchy and bureaucracy. - A career in a culture that rewards creativity and innovation, risk-taking and teamwork. Additional Information Our Core Values: Caring, Adaptable, Proactive Ownership, Empowering Clients Keywords: Shopify Plus, Shopify Hydrogen, BigCommerce Enterprise, BigCommerce Catalyst, Stencil, Headless Commerce, Composable Commerce, React, Next.js, Node.js, TypeScript, GraphQL, REST API, B2B Commerce, AI-Assisted Development, GitHub Copilot, Claude, Cursor, Codex, SSR, SSG, ISR, Core Web Vitals, OWASP, CI/CD, SonarQube, MCP, commercetools eCommerce & Marketplace Platforms: Shopify Plus, BigCommerce, commercetools, Adobe Commerce (Magento), Salesforce Commerce Cloud (SFCC), Mirakl Technology & Tools: CRM (Salesforce), PIM (Product Information Management), CPQ (Configure Price Quote), CMS (Content Management Systems), OMS (Order Management Systems), ERP (Enterprise Resource Planning), BI Tools (Business Intelligence) McFadyen's goal is to ensure that our clients are able to maximize the return on their technology investment by providing better service to their clients, partners and internal teams. At McFadyen we truly believe our employees are our most valuable asset. Across our locations in the US, Brazil, and India, we offer a world class work culture that enables top notch delivery for some of the world's most influential companies. McFadyen Digital is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, age, religion, sex, sexual orientation, gender identity / expression, national origin, disability, protected veteran status, or any other characteristic protected under federal, state, or local law, where applicable.