Senior Software Engineer

Xpansiv; City Of London; Hybrid; GBP 85,000 - 100,000; Full time

Job summary

A leading energy and environmental commodities firm in London seeks a Senior Software Engineer to maintain and develop financial systems using both legacy Microsoft technologies and PHP. Ideal candidates will have over 5 years' experience, strong skills in .NET Framework and SQL Server, and experience mentoring teams. The role supports a hybrid work environment and offers a salary range of £85,000-£100,000.

Qualifications

• 5+ years experience building web applications.
• Strong proficiency with SQL Server, including query optimization.
• Experience mentoring and leading a small team.

Responsibilities

• Develop secure, performance optimized and scalable code.
• Provide ongoing support, maintenance, and debugging for legacy applications.
• Collaborate with development and DevOps teams.

Skills

Web application development

.NET Framework

ASP.NET Web Forms / MVC

PHP

SQL Server

vanilla JavaScript

Mentoring

Education

B.S./M.S. in Computer Science or equivalent

Tools

GCP

AWS

Azure

Job description

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Xpansiv, a trailblazer in the energy and environmental commodities market, operates the integrated, open, and neutral market platform designed to accelerate the global energy transition. Xpansiv provides thousands of market participants and intermediaries with access to the widest possible range of energy transition markets, through its suite of solutions, including the world's largest environmental commodities trading platform, where billions of assets cross per year. Xpansiv's end-to-end technology platform services the entire life cycle of environmental commodities, connecting diverse markets and market participants across the world and enabling stakeholders to deliver transparent and trusted environmental claims to address the growing demand for energy transition. Leveraging its extensive industry knowledge and proven technology portfolio, Xpansiv assists companies seeking to identify and mitigate risk, streamline the management of their environmental assets, and comply with regulations, caps and commitments.

Overview

Position Summary: We are seeking a Senior Software Engineer with experience in both legacy Microsoft technologies and PHP. In this hybrid support/development role, you\'ll be the go-to expert for maintaining, troubleshooting, and extending mission-critical financial systems built on older tech stacks—while also interfacing with modern infrastructure. You will own this particular project and the team that maintains the development function for this application.

Responsibilities

• Develop secure, performance optimized and scalable code that is tested well documented.
• Provide ongoing support, maintenance, and debugging for legacy applications in production.
• Collaborate with development and DevOps teams to ensure stable deployment and operation of older systems.
• Investigate and resolve performance, stability, and integration issues.
• Write and optimize advanced SQL Server queries, stored procedures, and indexing strategies.
• Contribute to basic cloud administration.
• Understand and work within complex financial domain requirements, including compliance and security.
• Take ownership of the product and mentor junior staff.
• Participate in engineering efforts across the business as needed, primarily supporting PHP applications.

Required Qualifications

• B.S./M.S. in Computer Science or equivalent relevant experience
• 5+ years experience building web applications
• Strong proficiency with .NET Framework
• Strong proficiency with ASP.NET Web Forms / MVC
• Strong proficiency with Entity Framework
• Proficiency with PHP
• Hands-on experience writing and debugging vanilla JavaScript without relying on modern JS frameworks
• Experience mentoring and leading a small team of development engineers
• Expertise with SQL Server, including advanced features such as:
• Query optimization
• Indexing strategies
• Views, triggers, functions, and stored procedures
• Experience writing and consuming APIs

Preferred Qualifications

• Experience with modern frameworks such as .Net Core, ASP.NET Core and Entity Framework Core, as well as DevExtreme
• Experience with basic cloud infrastructure (preferably GCP, but AWS or Azure acceptable)
• Familiarity with CI/CD workflows and deployment pipelines is a plus
• Finance industry experience and understanding of financial products, regulations, or transaction workflows is a major advantage

Interview Process

1. Step 1 - Shortlisting of resume + recruiter screening
2. Step 2 - Technical take-home Assessment
3. Step 3 - Technical Interview with Engineers
4. Step 4 - Final interview with key stakeholders

Base Salary

Compensation for this role will vary among specific regions due to geographic differentials in the labor market, actual pay will be determined considering factors such as relevant skills and experience, knowledge, education and training. However, compensation in the following regions is expected to be as follows:

London: £85,000-£100,000

Note: At Xpansiv, we cultivate diversity, celebrate individuality, and believe unique perspectives are key to our collective success in building trust and transparency in global efforts toward net-zero future. Xpansiv is committed to equal employment opportunity regardless of race, color, religion, gender, sexual orientation, gender identity or expression, national origin, age, disability, genetic information, protected veteran status, or any status protected by applicable federal, state, or local law.

Note to Recruiters: Xpansiv does not accept unsolicited resumes or referrals from placement agencies, staffing vendors or other external parties seeking recruiting fees without a signed formal agreement.