Senior Kotlin Engineer (XP, GCP) – Investment Banking – London

Senior Kotlin Engineer (XP, GCP) – Investment Banking – London/Hybrid

Daily rate: £600 – £800 (inside IR35)

Duration: 6 months

Start: ASAP

My client is looking for an experienced Senior Kotlin engineer to support and extend a cloud-hosted platform used for bookbuilding issuances within Investment Banking Capital Markets. You will join a high-calibre London-based front office engineering team working on a next-generation issuance platform replacing a legacy bookbuilding system.

This is a hands-on engineering role with a strong emphasis on Extreme Programming (XP) practices, including mob programming, test-driven development, and continuous refactoring. Engineers are expected to contribute across development, integration, and production support, collaborating closely to maintain high standards of code quality, system reliability, and performance.

Required & Desirable Skills

• Strong commercial experience building backend services using Kotlin
• Experience with event-sourced and event-driven architectures
• Deep familiarity with XP practices, including:
• Mob programming as a primary way of working
• Test-driven development (TDD)
• Continuous refactoring and clean code principles
• Cloud experience with GCP, including:
• GKE and/or Cloud Run
• Cloud SQL and Memory store
• Artifact Registry and Cloud Logging
• Key Management
• Experience with CI/CD and SDLC in regulated or enterprise environments
• Comfortable working on production systems requiring high availability and accuracy

Engineers in this role:

• Work primarily in mobs, sharing ownership of design and code
• Build, test, and evolve services with a strong focus on clarity, simplicity, and maintainability
• Support the platform in production, using incidents and defects as opportunities to improve system design and resilience

*Rates depend on experience and client requirements