Senior Performance Test Engineer - C# .NET Gatling AWS
Posted 2 days ago by Lexstra Plc
£560 Per day
Inside
Hybrid
Richmond upon Thames, UK
Summary: Senior Performance Test Engineer with expertise in C# .NET, Gatling, and AWS is needed to lead the performance strategy across multiple product teams in a mature environment. The role involves maintaining and enhancing the performance platform, coaching engineers, and exploring AI tooling to improve performance processes. The position requires a hands-on approach rather than coordination, with a focus on building and demonstrating solutions. The working arrangement is hybrid, requiring two days on-site each week.
Key Responsibilities:
- Own the end-to-end performance strategy across 8-10 product teams.
- Maintain and enhance the in-house performance platform built on Gatling with a C# wrapper.
- Troubleshoot independently using tracing and metrics.
- Coach engineers directly within product squads.
- Explore AI tooling to reduce manual effort and accelerate issue detection.
- Drive performance improvements and shift performance left into CI/CD pipelines.
Key Skills:
- C# .NET
- Gatling
- k6
- JMeter
- OpenTelemetry/Splunk APM/Prometheus/Grafana
- AWS
- CI/CD
- SLI/SLO
- Distributed tracing
- Spark MCP
- Agentic AI
Salary (Rate): £560 per day
City: Richmond upon Thames
Country: UK
Working Arrangements: hybrid
IR35 Status: inside IR35
Seniority Level: Senior
Industry: IT
Senior Performance Test Engineer with C# .NET Gatling and AWS required to own the end-to-end performance strategy across 8 10 product teams in a mature, BAU performance environment, with a clear mandate to take it further.
Key skills: C# .NET, Gatling, k6, JMeter, OpenTelemetry/Splunk APM/Prometheus/Grafana, AWS, CI/CD, SLI/SLO, distributed tracing, Spark MCP and agentic AI.
The in-house performance platform is built on Gatling with a C# wrapper. You will maintain and enhance it, troubleshoot independently using tracing and metrics, and coach engineers directly within product squads rather than managing a dedicated performance team.
Around half your time will be enabling teams; the rest split between platform ownership and actively exploring how AI tooling particularly agentic workflows using Spark MCP and GitHub MCP can reduce manual effort, accelerate issue detection, and shift performance left into CI/CD pipelines. Splunk is the current observability stack; experience with Prometheus, Grafana, or Kibana is transferable.
You don't need to have delivered full agentic AI projects end-to-end, but you should be genuinely curious, self-directing, and able to put something tangible in front of teams quickly. This is not a coordinating role you'll be expected to build, demonstrate, and drive.
Hybrid: 2 days on-site (Wednesday & Thursday).