Job Description
Principal Trading Systems Architect – FIX & Execution (Capital Markets / Fintech)
Day Rate: €500–€600 per day
IR35: Outside IR35
Contract: 6 months initial (extension likely)
Location: London or Mainland Europe
Job Description
You'll be working for a well‑established capital markets participant modernising its electronic trading and execution infrastructure. The focus is firmly on FIX connectivity, low‑latency execution, and market‑making architecture, with live trading performance and stability as the non‑negotiables.
They are mid‑programme, migrating a legacy FIX estate into a modern Onix FIX‑based execution stack, and need senior expertise to guide architectural decisions, challenge assumptions, and ensure the platform is built correctly the first time.
This role exists because the work is business‑critical. The successful contractor will operate as a trusted senior advisor to trading and technology leadership — not a delivery‑only engineer.
The Role
This is a high‑impact senior advisory role, sitting at the intersection of trading, architecture, and execution performance.
You will:
- Act as the senior authority on FIX connectivity, execution flow and adapter design
- Define and guide the migration strategy from legacy FIX (e.g. ULLink) to Onix FIX
- Advise on market‑making, hedging and execution algorithm architecture
- Review and challenge existing design decisions with clarity and structure
- Translate complex technical trade‑offs into clear, concise guidance for senior stakeholders
- Influence platform direction without owning day‑to‑day delivery
- Work closely with traders, quants and senior engineers to align technology with trading intent
This role requires clear thinking, structured communication, and the ability to advise decisively, not just strong hands‑on engineering.
What We’re Looking For
- 5+ years commercial experience in Java and/or .NET within trading or capital markets environments
- Proven background in electronic trading systems, execution platforms or market‑making infrastructure
- Strong FIX connectivity experience (buy‑side or sell‑side)
- Demonstrated ability to operate in advisory, architecture‑led roles
- Experience explaining complex technical topics clearly to senior, non‑engineering stakeholders
- Low‑latency systems knowledge (threading, GC behaviour, performance trade‑offs)
- Prior exposure to South African markets or similar exchange environments is advantageous
Why This Role
- High‑trust, senior advisory engagement with real architectural influence
- Direct exposure to trading desks and decision‑makers
- Clear scope, urgency, and authority — no internal politics
- Fully remote, long‑term programme with extension potential
Apply
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