Senior Software Engineer - C# / Java

About Threecolts

Threecolts is the leading software suite for online & offline consumer brands (Amazon, Walmart, Target, Shopify, eBay, etc.). We’ve built a powerful ecosystem of software solutions to help businesses grow smarter — from revenue recovery and retail finance, to multichannel operations and pricing optimization. With over 500 employees globally and strong backing, we’re scaling fast across new markets and new partner channels.

We’re a global team built for speed, trust, and impact. As an AI enabled company, AI is integrated across Threecolts from development through to operations, empowering teams to move faster, build better, improve quality, and make more informed decisions. We hire exceptional people from all backgrounds and give them the autonomy to move fast and the accountability to deliver, where you will wear multiple hats, take ownership of challenges, and proactively solve problems beyond your immediate scope. Change is constant, ambiguity is part of the deal, and clear, concise communication is how we stay aligned, so when in doubt, bring people in.

Key Responsibilities

• You’ll take ownership of features across Inventory Lab’s C# and Java-based systems, delivering them from initial design through to production.
• You’ll design and build clean, scalable services, APIs, and components that are maintainable, well-tested, and performant.
• You’ll operate independently within a defined scope, making sound technical decisions and balancing speed with long-term quality.
• You’ll play an active role in improving the systems you work on, debugging production issues, identifying root causes, and implementing durable fixes.
• You’ll contribute to technical discussions, help evolve architecture within your domain, and raise the bar through thoughtful code reviews.
• Collaboration is key: you’ll work closely with Product, QA, and DevOps to build features and improvements that deliver meaningful value to Inventory Lab customers.

Qualifications

• 5–8+ years of professional software engineering experience
• Strong proficiency in C# and Java
• Experience building and maintaining backend services, APIs, and scalable application components
• Solid understanding of REST APIs, system design, and scalable application patterns
• Experience working with SQL databases and data modelling
• Familiarity with cloud infrastructure, ideally AWS
• Experience debugging production systems and resolving issues independently
• Comfortable working with Git, code reviews, and team-based development
• Ability to work across an existing codebase and improve quality without over-engineering
• You have a strong ownership mindset and consistently deliver high-quality work.
• You make pragmatic technical decisions, understanding when to prioritise speed and when to invest in scalability, reliability, and maintainability.
• You’re comfortable working in a product-led environment and care about the customer impact of what you build.
• You communicate clearly, work well with cross-functional teams, and look for ways to improve both the product and how the team operates.

In this role, you’ll support Inventory Lab, a product used by ecommerce sellers to manage inventory, listing, accounting, and operational workflows. The work will suit someone who enjoys solving practical product problems, improving reliability, and building systems that support real customer use cases.

Compensation, Perks & Benefits

• Salary: £90,000 per year
• 25 days PTO
• Opportunity to join company-wide offsites
• Regular rate reviews and bonus opportunities
• Fully remote/hybrid working