At a Glance
- Tasks: Design and build full-stack solutions while optimising for performance and scalability.
- Company: Join OnCommerce, a fast-growing global selling platform with a dynamic culture.
- Benefits: Competitive day rate of £450-£600, remote work, and hands-on ownership.
- Other info: UK remote role with excellent growth opportunities in a collaborative environment.
- Why this job: Be part of an innovative team shaping the future of ecommerce with real impact.
- Qualifications: Strong full stack engineering experience and familiarity with RESTful APIs and databases.
OnCommerce is a global selling platform that powers a growing network of retail channels, including:
- OnBuy - The only marketplace in the world to give customers instant Cashback on everything
- easyShop - An all-new marketplace created in collaboration with the easy® family of brands
- Comet - The iconic UK tech brand making its return later this year
OnCommerce is growing fast, launching new brands and scaling to power the future of ecommerce.
Be Part of the Story
OnCommerce is constantly evolving. Everyone here plays a hands‑on role in shaping what comes next, building brands that make an impact across global markets. There’s no red tape or rigid corporate structure; just smart people taking ownership and figuring things out as we build something big together. The pace is fast, priorities shift, things aren’t always perfectly set up, and you’ll often need to get stuck in and solve problems. But if you thrive in that kind of environment, you’ll have real influence, real ownership, and the chance to grow with a rapidly scaling business.
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
- 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
- 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
Experience
- Strong full stack engineering experience, owning end‑to‑end delivery
- Experience designing and building RESTful APIs and scalable systems
- Experience with MySQL and NoSQL 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 NoSQL (e.g. Couchbase) and Search platforms (e.g. Constructor & Solr)
- Experience working in microservices architecture
This role is UK remote role you must be based in the UK and have full right to work in the UK.
The day rate is £450-£600 per day. Please confirm your outside IR35 day rate upon application. This is a contract role until the end of August 2026.
Our Commitment
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.
Senior Full Stack Engineer CONTRACTOR - Contract from now until the 31st August employer: OnBuy
At OnBuy, we pride ourselves on being a dynamic and rapidly growing online marketplace that values each team member's contributions. Our work culture fosters collaboration and innovation, providing ample opportunities for personal and professional growth in a fast-paced environment. As a Senior Performance Marketing Manager, you'll play a pivotal role in shaping our marketing strategies while enjoying the benefits of a supportive team that encourages meaningful change and prioritises your voice.
StudySmarter Expert Advice🤫
We think this is how you could land Senior Full Stack Engineer CONTRACTOR - Contract from now until the 31st August
✨Make Your Portfolio Shine
As a freelancer in software development, your portfolio is your bread and butter. Showcase not only your completed projects but also your coding skills on platforms like GitHub or GitLab. This visibility can lead to clients reaching out to you directly!
✨Join Developer Communities
Get involved in developer communities like Stack Overflow or Reddit's r/programming. Contributing to discussions, sharing your knowledge, or even helping others can expand your network and lead to freelance opportunities. Plus, it keeps you in the loop about what’s trending in software development.
✨Freelance Platforms Are Your Friend
Sign up for popular freelance platforms such as Upwork or Freelancer. They’re filled with people looking for talent like yours! Don’t forget to personalise your pitch to each potential client, highlighting how your unique skills can solve their specific problems.
✨Utilise Your Network
Don’t hesitate to reach out to your existing contacts - you never know who might need your services or can refer you to someone who does. Personal connections can lead to more reliable gigs than cold applications. And we're here to help too! If you're looking for freelance opportunities, check out opportunities listed on our website.
We think you need these skills to ace Senior Full Stack Engineer CONTRACTOR - Contract from now until the 31st August
Some tips for your application 🫡
Showcase Your GitHub Projects:When applying for a freelance software engineering gig at OnBuy, make sure to include your GitHub link in your application. Highlighting your code repositories, contributions to Open Source, and any personal projects can really set you apart and give us insight into your skills and coding style.
Tailor Your CV with Relevant Skills:In software development, the specifics matter! Make sure your CV lists the programming languages and technologies you excel at. Focus on the ones that align with the projects OnBuy is working on. Listing your tech stack clearly will help us understand how you fit into our team.
Include a Portfolio of Your Work:A solid portfolio is a must when applying for freelance roles. Include links to any apps, websites, or software you've developed. Highlight any projects that reflect a strong user experience, efficiency, or innovative solutions—this is your chance to shine and show us what you can bring to the table!
Mention Your Availability and Rates:Since this is a freelance role, we want to know when you’re available and what your rates are like! Be upfront about your typical work hours and project timelines. This transparency will help us see if we can sync up for future projects at OnBuy.
How to prepare for a job interview at OnBuy
✨Showcase Your Code Wizardry
Since you're going for a freelance role in software engineering, have a solid portfolio ready to flaunt your best work. Include projects that highlight your coding skills, frameworks you excel in, and any problem-solving feats you've pulled off. This is your chance to shine, so choose pieces that reflect your unique style and expertise!
✨Prepare for Technical Challenges
Freelance gigs often involve tech assessments or coding challenges, so be ready to tackle some hands-on problems. Brush up on common algorithms, data structures, and any languages/frameworks relevant to the role at OnBuy. Being comfortable with platforms like HackerRank or LeetCode can give you an edge and showcase your skills under pressure!
✨Be Clear About Your Rates and Flexibility
As a freelancer, be prepared to discuss your rates upfront. It's crucial to communicate your pricing structure clearly and whether you're open to negotiation. Do your homework on industry standards to ensure you pitch a fair and competitive rate that reflects your skills and experience!
✨Understand Their Tech Stack
Before the interview, get familiar with the tools and technologies used at OnBuy. Whether it's a particular framework or a specific coding methodology, being knowledgeable about their tech stack not only shows your interest but also helps you present how you could fit seamlessly into their existing projects. Demonstrating you’ve done your homework can set you apart from other candidates!
