Principal Software Engineer | C# .NET Energy Trading | ETRM Architectural Redevelopment | Azure | £120,000 | 3 days in office | London

Our client, a leading global energy brokerage, is looking for a Principal C# .NET Software Engineer to join their Power and Gas team for a crucial restructuring of their Front Office ETRM trading platform. This isn’t a maintenance role you will be driving a major architectural redesign of a C# .NET‑based ETRM system that underpins a high‑performing trading desk. You will act as the key technical authority, taking ownership of a low‑latency C# .NET trading platform operating across Power and Gas markets.

What makes this role unique is the cause‑and‑effect nature of the system: every action your code takes influences market behaviour, and the market immediately feeds back into your platform. This requires engineering judgement in real time — handling asynchronous events, mutating state safely, and ensuring the platform remains deterministic under volatility.

In this role, you will own the full‑stack restructuring of a low‑latency ETRM platform, applying deep C# .NET architectural expertise to deliver a real‑time, event‑driven trading system. You will design a scalable C# .NET trading architecture capable of supporting increased user concurrency, complex pricing logic, P&L workflows, and execution management as the desk expands across Power, Gas, and Emissions trading.

The current system is a legacy C# ETRM platform built for a small user base; the challenge is to evolve it into a resilient, event‑driven C# .NET trading system capable of supporting multiple Front Office traders interacting with live market data, reacting to execution events, and recalculating P&L and risk in real time. This demands strong command of asynchronous C# workflows, event‑driven architecture patterns (Kafka / Solace), queuing and pipeline design, and clean separation between trading logic, execution services, APIs, and UI layers.

You will bring first‑hand experience designing high‑performance C# .NET trading systems where correctness, determinism, latency control, and throughput are essential. Drawing on best practices from Front Office Energy Trading, you will ensure the ETRM platform can absorb volatility, scale horizontally, and maintain predictable behaviour under stress. This is an opportunity to influence not only the C# .NET architecture, but the broader Energy Trading technology strategy balancing low latency, resilience, scalability, and long‑term maintainability.

Salary: £120,000 + performance bonus

Location: London (Hybrid)

Tech Stack: C# | .NET 8 | Azure | On‑Prem | Angular | Kafka | SQL Server | gRPC | REST APIs | Event‑Driven Architecture

Technical Requirements

Front Office Pedigree: 8+ years in high‑performance C# .NET environments, specifically building P&L, Risk, Pricing, or ETRM trading systems within Energy Trading.

Messaging Expertise: Deep experience with high‑throughput messaging systems (Kafka / Solace), implementing asynchronous, event‑driven C# architecture patterns and handling real‑time state mutation.

Architectural Leadership: Proven ability to design and build scalable C# .NET trading platforms while maintaining clean architecture, SOLID principles, and long‑term maintainability.

Database Fundamentals: Strong SQL Server experience managing high‑volume trading data, audit trails, trade capture, and real‑time reporting within an ETRM or Energy Trading platform.

Communication: Ability to work closely with Front Office stakeholders, traders, quants, and technology teams to define and architect scalable C# .NET ETRM solutions aligned to business growth.