Senior Software Engineer - Kotlin

Senior Software Engineer - Kotlin

£550-£650 per day | Outside IR35

Hybrid | London (3 days onsite)

A leading UK financial services organisation is seeking a Senior Software Engineer to play a central role in a large-scale platform transformation programme. The business is rebuilding a critical part of its digital infrastructure to support a broad range of transaction methods and channels across both in-person and digital environments.

This is hands-on Back End engineering at scale, with real ownership and direct exposure to architecture decisions from day one.

Key Responsibilities as a Senior Software Engineer

• Design and build Kotlin Back End services for a new payments platform
• Own the architecture and design of key components, taking high-level requirements and turning them into structured, deliverable backlogs
• Write clean, well-tested, production-ready code that the team can rely on
• Work closely with Product and Engineering to break down complex problems and ship impactful features
• Bring fresh thinking to existing approaches and propose improvements where you see them
• Support team leadership across delivery, code quality, and technical decision-making
• Contribute to technical hiring, helping to assess and attract strong engineering talent

Skills & Key Requirements

• Strong commercial Kotlin experience for Back End development, ideally within payments or financial services
• Domain expertise in payment gateway systems or payments infrastructure
• Comfortable with React.js for full stack contribution where required
• Proven ability to take requirements through to architecture, design, and delivery
• Senior Software Engineer level ownership of technical decisions and delivery
• Clear grasp of software engineering fundamentals: design patterns, SOLID principles, test-first design
• Familiarity with Agile practices including peer code review and pair programming
• Hands-on exposure to AWS or comparable cloud platforms
• Background in both monolithic and microservices-based systems
• Experience in a product-led environment where engineering and business goals are closely aligned

Contract Details

• Day rate: up to £650 per day
• IR35: Outside IR35
• Contract length: 6 months initial term, extension likely
• Location: London, hybrid (3 days onsite)
• Start: ASAP

If you are a Senior Software Engineer with strong Kotlin Back End experience and interested in working in the financial services space, apply now or reach out directly to find out more.

Due to the high volume of applications, not all applicants will receive feedback.