Principal Consultant in London

We are looking for a senior technical leader to help drive the evolution of a complex, business-critical trading platform within a tier-one investment bank. This role is focused on understanding an existing legacy system — rich in workflow, automation, pricing, booking, and client connectivity — and defining a clear, practical technical roadmap that delivers immediate business value while steadily moving the platform toward its long-term strategic architecture.

You will work closely with engineering teams, quant partners, and senior stakeholders to assess how the platform operates today, including nuanced pre-trade and post-trade flows and bespoke, client-specific FIX implementations. A target architecture is also being defined in parallel, and a key part of this role is evolving the current stack so that it is ready to be migrated to the new platform — identifying dependencies, reducing unnecessary complexity, and ensuring the transition can happen incrementally without disrupting live trading.

This is not a greenfield role. Success comes from adding value immediately within a large, demanding codebase — understanding existing Java and .NET systems well enough to reason about trade-offs, guide refactoring or selective rewrites, and make sound architectural decisions under pressure. The roadmap you produce is as important as the changes themselves.

A strong candidate will actively embrace agentic AI tooling as a force multiplier — not just to accelerate development, but to rapidly comprehend unfamiliar systems, trace behaviour across services, uncover hidden dependencies, and validate architectural thinking. Combined with deep equities domain knowledge and experience building large-scale distributed systems, this role offers the chance to spearhead meaningful, pragmatic change within a high-impact trading environment.

• Ability to assess complex legacy systems, define pragmatic technical roadmaps, and drive incremental modernization toward a strategic target platform.
• Experience delivering incremental modernization of live, revenue-critical systems under active business demand.
• Experience preparing legacy systems for migration to a target architecture, including dependency analysis, interface stabilisation, and incremental decoupling.
• Strong knowledge of the investment banking domain, with hands-on experience in equities pre-trade and post-trade systems.
• Experience integrating and supporting front-office, in-house quantitative libraries developed by desk quants within production environments.
• Proactive in using agentic AI tools to accelerate understanding of large, unfamiliar codebases and complex system behaviour, not just development.
• Comfortable reading and reasoning about large Java and .NET codebases to inform architectural decisions, modernization strategy, and platform transition planning.

London-based, with on-site presence required 3 days per week minimum.

• Experience with FIX protocol and client connectivity patterns.
• Familiarity with message brokers (Kafka, Solace) and event-driven architectures.
• Prior consulting experience or comfort operating across multiple stakeholder groups.

This role is hybrid - with on-site presence required 3 days per week minimum in London, Canary Wharf.

Both permanent and contract arrangements considered.

We can only consider candidates who have the right to work in the UK and do not require visa sponsorship. Applicants must be UK-based and within a commutable distance to London.

Interested? Email careers@juxt.pro with your CV and a brief introduction. Even if you are not sure you tick every box, we would still love to hear from you - we are always keen to meet passionate, technically curious developers and engineering leads and can keep you in mind for future projects if this one isn’t the right fit.