Javascript Developer Remote Internship Jobs in Fairfax, VA

McFadyen Digital is the leading advisor and implementer of eCommerce Marketplace solutions. During 15 years of implementing marketplaces, we’ve built dozens of platforms that cumulatively generate billions of dollars of gross merchandise value (GMV). We’re honored to have supported 10% of the Fortune 500 with their digital marketplace initiatives. Over 250 global brands like ABB, AB InBev, ACCO, Albertsons, American Red Cross, American Eagle Outfitters, US Army, US Agriculture Dept, (and many more) have entrusted their digital transformations to McFadyen. We operate global offices across the US, Brazil, and India. McFadyen Digital has been a trusted employer for over 39 years and believes that people are the most important part of our company. We’re proud of our Great Place to Work certification.

Learn more about us at our website: www.mcfadyen.com

We’re looking for a Senior Full-Stack Developer — with a strong backend focus — to join a fast-moving marketplace project on a short-term contract basis. You’ll design and build composable commerce services on commercetools and stand up seller and catalog flows through Mirakl’s dropship model, integrating the two into a seamless buyer and seller experience. This is a hands-on delivery role for an engineer who can own backend architecture, ship production-grade APIs and integrations quickly, and contribute to the frontend where needed. If you thrive in headless, API-first environments and want high-impact work with clear deliverables over a defined engagement, this role is for you.

• Engagement type: Independent contractor (project-based).
• Duration: 3–4 month project engagement, with potential to extend based on project needs.
• Availability: Full-time (40 hours/week) for the duration of the engagement.
• Location / work model: Fully remote. Open to candidates based in the US, Latin America (LATAM), or Canada, with meaningful overlap with US business hours.
• Start: September/2026

Top 5 Responsibilities

1. Design, build, and maintain scalable backend services and APIs on commercetools to power catalog, cart, checkout, and order flows in a headless, composable architecture.
2. Implement and configure Mirakl dropship capabilities — seller onboarding, offer and catalog ingestion, order routing, and shipment/tracking workflows — and integrate them with commercetools and downstream systems.
3. Develop robust, secure integrations between commercetools, Mirakl, and third-party systems (OMS, ERP, PIM, payment, and shipping providers) using REST, GraphQL, webhooks, and event-driven patterns.
4. Deliver production-ready code on an aggressive project timeline, including automated tests, error handling, logging, and documentation suitable for handoff at the end of the engagement.
5. Collaborate with architects, product, and frontend engineers to translate requirements into technical solutions and contribute frontend work (React/Node) where the project requires it.

Additional Responsibilities

• Build and maintain commercetools extensions, subscriptions, and API clients; manage project settings, types, and custom fields.
• Configure Mirakl connector flows and reconcile marketplace data (offers, orders, messaging, and payouts) with the commerce platform.
• Optimize performance, reliability, and scalability of backend services and integration points.
• Participate in code reviews, technical design discussions, and daily agile ceremonies (standups, sprint planning, retrospectives).
• Troubleshoot and resolve production and integration issues quickly during the engagement.
• Document architecture, integration specs, and runbooks to ensure a clean transition to the client/internal team at project close.

Top 5 Qualifications

1. 6+ years of professional software engineering experience, with a primary focus on backend development (Node.js and/or Java) in production eCommerce environments.
2. Hands-on, demonstrable experience building on commercetools (APIs, projects, extensions, subscriptions, and composable/headless commerce patterns).
3. Practical experience implementing Mirakl — specifically the dropship model — including seller/catalog/offer ingestion and order and shipment workflows.
4. Strong integration expertise: REST and GraphQL APIs, webhooks, event-driven architecture, and connecting commerce platforms to OMS/ERP/PIM and payment/shipping providers.
5. Full-stack capability with enough frontend proficiency (React, TypeScript, JavaScript) to contribute to UI work when needed.

Additional Qualifications

• Bachelor’s degree in Computer Science or a related field, or equivalent practical experience.
• Experience with cloud platforms (AWS, Azure, or GCP) and CI/CD pipelines (Docker, Kubernetes, or similar).
• Familiarity with marketplace business models, seller operations, and dropship fulfillment.
• Solid grasp of API security, authentication/authorization, and data privacy best practices.
• Experience delivering under contract or consulting engagements with tight, well-defined timelines.
• commercetools and/or Mirakl certification is a plus.
• Comfortable working independently in a remote, distributed, agile team.
• Excellent written and verbal English communication skills.

Our Core Values: Caring, Adaptable, Proactive, Empowering Clients

Keywords: Full-Stack Developer, Backend Developer, commercetools, Mirakl, dropship, marketplace, composable commerce, headless commerce, Node.js, Java, React, TypeScript, API integration, GraphQL, eCommerce, contractor, remote job

Equal Opportunity Employer

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.