Senior Full Stack Engineer Contractor

The Role 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

• 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

• 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

• 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

• Optimise systems for performance, reliability, and scale
• Work with large-scale data systems (MySQL, No
  
  SQL, search platforms)
• Identify bottlenecks and proactively improve system efficiency

• 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

• Strong full stack engineering experience, owning end-to-end delivery
• Proven backend expertise in PHP (Laravel)
• Strong JavaScript (ES6+) skills with modern frameworks (React/Vue/Angular)
• Experience designing and building RESTful APIs and scalable systems
• Experience with MySQL and No
  
  SQL databases (e.g. Couchbase, MongoDB)
• Strong understanding of system architecture and microservices
• Experience with event-driven systems (e.g. RabbitMQ, Pub/Sub) and cloud environments (GCP)
• Familiarity with Docker and CI/CD pipelines
• Strong engineering practices: testing, code quality, and production ownership

• Experience in eCommerce or marketplace platforms
• Cloud experience (GCP)
• Experience with No
  
  SQL (e.g. Couchbase) and Search platforms (e.g. Constructor & Solr)
• Experience working in microservices architecture

This role is UK remote; you must be based in the UK and have full right to work in the UK.

The day rate is £450- £600 per day. DOE Please confirm your outside IR35 day rate upon application. This a contract until the end of August 2026.

OnBuy is an equal opportunities employer. We are dedicated to creating a fair and transparent workforce, starting with a recruitment process that does not discriminate on the basis of gender, sexual orientation, marital or civil partnership status, pregnancy or maternity, gender reassignment, race, colour, nationality, ethnic or national origin, religion or belief, disability, or age.