Senior Kotlin Engineer; XP, GCP – Investment Banking

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 book building 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 book building 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.

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

• 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), and 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

* Rates depend on experience and client requirements