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Prepare system-design and full-stack trade-offs (consistency, latency, auth, observability), live coding across UI and API layers, and concrete stories of shipping and debugging multi-service features under time pressure.
Strong fit if you are a senior full-stack engineer comfortable contracting in the UK, owning features end-to-end, and working on-site or hybrid rather than fully remote.
As a Senior Full Stack Engineer Contractor at OnBuy, expect end-to-end ownership: design and ship features across frontend and backend, review PRs, harden APIs and UI for production traffic, and pair with product/ops on delivery. Days skew toward scoped tickets, incident follow-ups, and reliable releases rather than greenfield-only work.
Strengthen TypeScript/JavaScript, a modern web framework, API design, relational data, testing, and cloud deploy/debug habits. No certification list was supplied for this posting; prioritize portfolio depth and production ownership over paid certs.
The listing marks remote as no; expect United Kingdom-based work rather than fully remote.
You are engaged as a contractor senior full-stack engineer—delivery-focused ownership of web features, not a permanent headcount guarantee.
Only the employer domain onbuy.com is provided; treat other company claims outside the posting as unverified.
Website: onbuy.com
Public cache only — not an employee review.
OnBuy, part of the fast-growing OnCommerce family of marketplaces, is looking for a Senior Full Stack Engineer Contractor to take end-to-end ownership of features across a high-traffic ecommerce platform. This is a UK-based remote contract role for an engineer who thrives on ownership, pace, and building things that ship. About the Role As a Senior Full Stack Engineer Contractor at OnBuy, you will design, build, and maintain complete solutions spanning user interfaces, APIs, and backend systems. You will turn product requirements, designs, and wireframes into scalable, production-ready software, owning each feature from initial concept through development, testing, release, and ongoing monitoring. You will work across both monolith and microservices architectures while modernising and evolving existing systems. Key Responsibilities Deliver full-stack features end to end, taking ownership from idea through to production and monitoring. Develop responsive, high-performance interfaces with modern JavaScript frameworks, translating UI/UX designs into clean, maintainable code. Architect and build scalable services and RESTful APIs across Laravel/PHP monolith and microservices environments. Maintain and gradually modernise legacy systems alongside new, scalable architecture. Embed quality throughout delivery by writing and maintaining unit, integration, and end-to-end automated tests. Lead and contribute to code reviews, debug issues across the stack, and uphold strong engineering standards. Tune systems for performance, reliability, and scale while working with large datasets in MySQL, NoSQL, and search platforms. Collaborate with Product, Design, QA, and fellow engineers, mentor junior team members, and explain technical concepts to non-technical stakeholders. Qualifications Extensive full-stack experience with proven ownership of end-to-end delivery. Strong backend expertise in PHP and the Laravel framework. Advanced JavaScript (ES6+) skills with a modern framework such as React, Vue, or Angular. Hands-on experience designing RESTful APIs and scalable, well-architected systems. Working knowledge of MySQL alongside NoSQL databases such as Couchbase or MongoDB. Solid grasp of system architecture, microservices, and event-driven systems like RabbitMQ or Pub/Sub. Experience with cloud environments (GCP), Docker, and CI/CD pipelines. Desirable: a background in ecommerce or marketplace platforms and exposure to search platforms such as Constructor and Solr. About OnBuy OnBuy is the only marketplace in the world to offer customers instant Cashback on everything,…
Generated for personal interview prep · 2026-07-17 UTC · getajob.ai