Role summary by JobGrid
Senior Full Stack Engineer Contractor at OnBuy: Remote, United Kingdom; Contract; Senior; IT; Full Stack Engineer. This listing is part of JobGrid's Remote software engineer jobs from public company career pages. JobGrid adds normalized role facts, source context, and a path to the employer application page so candidates can compare the listing before applying.
- Location and workplace: Remote, United Kingdom
- Role classification: IT, Full Stack Engineer, Contract, Senior
- Source freshness: checked by JobGrid on 2026-05-28.
- Application path: candidates continue to the employer application page with non-personal referral tags.
Who are OnBuy?
OnBuy are an online marketplace who are on a mission of being the best choice for every customer, everywhere.
We have recently been named one of the UK's fastest-growing tech companies in the Sunday Times 100 Tech list.
All achievements we are very proud of, but we don't let that go to our head. We are all laser focused on our mission and understand the huge joint effort ahead of us needed to succeed.
Working at OnBuy:
. This is a critical role responsible for building, scaling, and evolving OnBuy’s core commerce platform across both front-end and back-end systems. As a Senior Full Stack Engineer, you will own engineering delivery end-to-end; from customer-facing experiences to underlying services and data systems. You will operate within a cross-functional team and be accountable for shipping high-quality, scalable solutions that directly impact GMV, seller performance, and customer experience. This role moves beyond “front-end vs back-end” you are an Engineer responsible for outcomes, not layers.
End-to-End Engineering Ownership
- Design, build, and maintain full-stack solutions across UI, APIs, and backend systems
- Translate product requirements, designs, and wireframes into scalable, production-ready systems
- Own features from concept → development → testing → release → monitoring
Front-End Excellence
- Build responsive, high-performance user interfaces using modern JavaScript frameworks
- Translate UI/UX designs into clean, maintainable code
- ·Optimise applications for speed, scalability, and usability
Back-End & Platform Engineering
- Design and develop scalable services and APIs
- Work across monolith and microservices architecture (Laravel / PHP services)
- Maintain and evolve legacy systems while building modern, scalable architecture
Quality & Engineering Standards
- Own quality to production — testing is embedded, not a phase
- Write and maintain automated tests (unit, integration, end-to-end)
- Participate in and lead code reviews to ensure high engineering standards
- Debug, troubleshoot, and resolve issues across the stack
Performance & Scalability
- Optimise systems for performance, reliability, and scale
- Work with large-scale data systems (MySQL, NoSQL, search platforms)
- Identify bottlenecks and proactively improve system efficiency
Collaboration & Leadership
- Work in cross-functional teams with Product, Design, QA, and other Engineers
- Mentor and support less experienced engineers
- Communicate technical concepts clearly to non-technical stakeholders