Senior / Principal Kotlin Engineer

JUXT; Greater London; On-site; GBP 70,000 - 110,000; Full time

Benefits offered by this job

25 days holiday

Job summary

JUXT in London is hiring several Kotlin developers ranging from senior to principal levels to join long-term greenfield projects with leading financial institutions. You will work in small, high-calibre teams building new services and modernising legacy systems, ensuring scalable architecture and quality code.

The role emphasizes hands-on coding, architectural input, and real ownership with minimal BAU. You will gain exposure to large-scale distributed systems in a collaborative, trust-based

Qualifications

• Strong Kotlin skills with depth in modern engineering practices (TDD, clean code, SOLID).
• Designing scalable, mission-critical systems with end-to-end testing.
• Ability to work in a collaborative, high-autonomy environment.
• Experience with greenfield builds or legacy replacement.

Responsibilities

• Develop Kotlin-based services for long-term greenfield initiatives in London.
• Collaborate with engineers to shape architecture and deliver end-to-end solutions.
• Write high-quality code and participate in architecture decisions.

Skills

Kotlin

System design

End-to-end testing

Autonomy

Greenfield development

Problem solving

Job description

We are looking for several Kotlin developers, from experienced seniors to hands-on principal engineers, to join long-term greenfield projects with leading financial institutions in London.

You will be part of small, high-calibre engineering teams delivering strategic rebuilds and modernisation projects, replacing legacy systems with clean, cloud-aligned solutions built on Kotlin and modern engineering practices. These are not maintenance roles - they are about writing great code, solving challenging problems, and shaping architecture from the ground up.

You will be joining teams working on genuinely greenfield, strategic rebuilds with clear scope, autonomy, and modern tech stacks. There is little to no BAU work, and plenty of room to shape architecture, influence direction, and own your contributions end-to-end.

This is a great opportunity to deepen your Kotlin expertise, work alongside highly capable engineers, and gain exposure to large-scale systems and distributed architectures within major financial organisations with no prior banking experience required.

This is a collaborative, trust-based environment where developers have real autonomy, clear ownership, and meaningful technical input. There is a genuinely friendly culture in the team - people take pride in their craft and support each other to deliver excellent software.

Core Skills

• Strong Kotlin skills, with depth in modern engineering practices (TDD, clean code, SOLID principles)
• Demonstrated knowledge and hands‑on experience in designing scalable, mission-critical systems
• Strong understanding of system integration and end‑to‑end test design principles
• Ability to work effectively in a collaborative, high‑autonomy environment
• Experience with greenfield builds and/or incremental legacy replacement
• Strong problem‑solving ability and architectural reasoning
• Hands‑on mindset 6 this is a coding role first and foremost

Nice To Have

• Experience with large‑scale data processing or distributed query systems (e.g. Spark, Beam, Flink, Trino, Presto, Hive, etc.), or the ability to quickly pick up similar tools
• Exposure to financial services or enterprise‑scale systems

Company Benefits

• 25 days holiday

Interview Process

• 1 - Interview with one of the Talent Acquisition Team
• 2 - All in One interview (tech test and Q+A) with a current JUXT employee
• 3 - Interview with the client (technical)