Principal Software Engineer

Principal Engineer / Architect (.NET / Azure)

Location: Hybrid – London (1–2 days per month)

Salary: £100,000- £110,000 (depending on experience)

Team: Core Engineering Team – Agile / Kanban

Overview

Our client is a high-growth SaaS scale-up transforming the world of money transfer and payments.

Following consistent year-on-year revenue growth and successful funding, the business is entering its next phase of international expansion.

To support this growth, they are seeking a Principal Engineer / Architect to join their Core Engineering Team—someone with strong architectural capability, but who remains highly hands-on in development.

This role is ideal for a senior technologist who can design and shape scalable platform architecture while still being deeply involved in coding, engineering delivery, and solving complex technical problems.

You will play a key role in scaling a modern platform that supports high-volume, real-time payments and financial transactions across a rapidly expanding global customer base.

We are specifically looking for someone with proven experience building high-transaction financial systems, including payments, banking, money transfer, or regulated FinTech platforms.

The Role

As Principal Engineer / Architect, you will work closely with the CTO and senior leadership team to define technical strategy, platform architecture, and engineering best practice across the business.

You will take ownership of designing scalable, secure, high-performance systems while also remaining hands-on in the delivery of key services and complex engineering challenges.

This is not a pure architecture role—we need someone who still enjoys writing production-grade code, mentoring engineering teams, and leading from the front technically.

The engineering team operates using a Kanban-based Agile model with continuous delivery, enabling rapid iteration and deployment of new features.

This role suits someone who can balance strategic architecture with practical delivery and has operated successfully within fast-paced, high-growth FinTech or payments environments.

Key Responsibilities

• Architect and enhance .NET Core 9/10 applications and microservices supporting real-time payment processing
• Design secure, scalable, low-latency backend architectures for high-volume financial transaction platforms
• Lead technical decisions across API-led distributed systems and event-driven architecture
• Build and scale integrations supporting money transfers, card payments, savings functionality, and Mastercard integration

Work across a modern Azure SaaS stack including:

• Azure SQL
• Azure Blob Storage
• Azure Redis
• Azure Service Bus
• Azure Front Door
• Improve platform resilience, observability, scalability, and operational excellence
• Collaborate closely with Operations to improve automation and reduce third-line support overhead
• Contribute to BAU operational tickets where required (~10–15%)
• Mentor senior developers and help elevate engineering standards across the team
• Support the CTO in defining long-term technical strategy and platform evolution
• Operate within a Kanban-based Agile environment focused on continuous delivery

Required Experience

• Extensive C# / .NET Core (9/10) development experience
• Proven experience operating at Principal Engineer, Lead Developer, or Solution Architect level while remaining hands-on
• Strong architectural design experience across distributed systems and microservices
• Experience designing RESTful API-led architectures
• Proven experience working with high-volume OLTP systems
• Strong background building low-latency, real-time payment, banking, financial services, or money transfer platforms
• Strong experience designing solutions using Microsoft Azure cloud services
• Strong MS SQL expertise and relational database design knowledge
• Experience with event-driven systems and asynchronous processing patterns
• Agile / Kanban development experience with a continuous delivery mindset
• Strong experience using Azure DevOps and Git

Desirable Experience

• Angular front-end development
• Infrastructure as Code (IaC) on Azure
• Mobile development using .NET MAUI (iOS / Android)
• Experience working within SOC 2 or ISO 27001 environments
• Experience within software consultancies, software houses, or distributed international development teams
• Experience leading architecture reviews, technical governance, and engineering standards

What’s on Offer

• Flexible working hours and hybrid working
• Competitive salary, bonus, share scheme and benefits
• 33 days holiday (including bank holidays)
• Company laptop, PC or Mac (with Parallels)
• Rewards scheme with discounts across retail, hospitality, services and much more
• Expenses covered for travel/events
• The opportunity to work from anywhere – including up to 4 weeks abroad each year
• Clear career progression in a rapidly growing business
• The chance to work and collaborate with a team featuring a number of former consulting professionals
• Regular social events

If you’re interested in building scalable FinTech platforms and shaping architecture within a high-growth SaaS environment, we’d love to hear from you.

Unfortunately, our client are unable to provide sponsorship for this role.

Our client is committed to promoting Diversity, Equity, and Inclusion across all areas of their business. They strive to ensure fair and inclusive hiring practices that reduce bias, widen talent pools, and create opportunities based on skills, potential, and values. They believe that diverse teams create stronger businesses, better decision-making, and long-term success.