Senior Back-End Developer (.NET)

REMIUM; City Of London; On-site; GBP 90,000 - 130,000; Full time

Job summary

REMIUM, a London-based fintech, seeks a Senior Back-End Developer to own and evolve our .NET microservices stack. You will design, implement, and optimize robust backend services for payments, FX, and treasury workflows, ensuring correctness, security, and resilience at scale.

You will guide a growing in-house engineering team, mentor peers, and contribute to DevOps efforts on GKE, PostgreSQL, and Redis within a regulated payments environment.

Qualifications

• Extensive experience building production back-end systems in C# / .NET.
• Strong API design skills (REST) and inter-service communication.
• Proven ability to lead, mentor, and raise engineering standards.

Responsibilities

• Lead the design, development, and maintenance of .NET microservices from API design to data modelling.
• Drive code quality, architectural coherence, and reduce technical debt across services.
• Design robust services for payments, FX, and treasury workflows with emphasis on correctness and security.
• Work with PostgreSQL and Redis for transactional data and caching with performance in mind.
• Improve GitLab CI/CD pipelines, automated testing, and safe release practices.
• Mentor developers and collaborate with DevOps on observability and secure deployment to GKE.
• Support regulatory and banking partner requests with technical input as needed.
• Demonstrate leadership by example through code reviews and pragmatic decisions.

Skills

C# / .NET

REST APIs

PostgreSQL

Redis

Kubernetes / GKE

GitLab CI/CD

Mentoring

Cloud platforms

Security & compliance

Leadership

Tools

GitLab

Kubernetes

Google Cloud Platform (GCP)

Docker

Job description

REMIUM is a financial services company built to serve global businesses and individuals with seamless local and cross-border payment infrastructure. From Family Offices and payroll businesses to SaaS providers and E-commerce operators, our clients trust us to simplify international payments, FX, treasury, and financial operations within a fully compliant digital ecosystem.

By combining powerful digital tools with high-touch, human-led support, we deliver a service designed for the complex realities of global finance. Headquartered in London, we’re building the next generation of payments infrastructure that empowers ambitious businesses and individual clients alike.

This is your chance to join a fast-scaling fintech at the intersection of payments, FX, and private client services, and play a key role in shaping our growth story.

Role Summary

We are looking for a Senior Back-End Developer to become the technical anchor of our newly forming in-house engineering team.

Our platform is built on a suite of .NET microservices, backed by PostgreSQL and Redis, running on Google Cloud Platform (GKE) and delivered through GitLab CI/CD. You will take deep ownership of this codebase: leading its ongoing development, raising engineering standards, and guiding the work of other developers as the in-house team grows.

This is a senior, high-influence role in a regulated payments business. The services you build and harden move real money; correctness, resilience, and security are not nice-to-haves here, they are the job.

Key Responsibilities

• Lead the design, development, and maintenance of our .NET microservices, from API design through to data modelling and integration
• Take ownership of the codebase: drive code quality, architectural coherence, and technical debt reduction across services
• Design robust, well-tested services for payments, FX, and treasury workflows, with strong attention to correctness, idempotency, and auditability
• Work with PostgreSQL and Redis for transactional data and caching, with an eye on performance and integrity
• Contribute to and improve GitLab CI/CD pipelines, including automated testing, quality gates, and safe release practices
• Mentor and review the work of other developers, in-house and external, setting the bar for engineering standards
• Collaborate with our DevOps function on observability, reliability, and secure deployment onto GKE
• Build with security and regulatory expectations in mind, and support audit and banking partner requests with technical input where needed
• Extensive commercial experience building production back-end systems in C# / .NET, including microservice architectures
• Strong API design skills (REST) and experience with inter-service communication patterns, messaging, and resilience techniques
• Deep working knowledge of PostgreSQL (schema design, query performance, transactions) and practical experience with Redis
• Experience running containerised services in Kubernetes; GKE experience is a plus
• Solid grounding in automated testing and CI/CD; GitLab experience is advantageous
• A track record of leading by example: raising standards through code review, mentoring, and pragmatic technical leadership
• Experience in payments, fintech, or another regulated environment is strongly advantageous
• Clear communication skills and the judgement to make sound technical decisions in a small, fast-moving team

Why REMIUM?

At REMIUM, we’re not just building a payments company, we’re building a trusted network for global businesses and individual clients. Every client you support helps bridge global finance with a human, personal touch.

We believe in empowering our people, celebrating individual contributions, and creating an environment where ambition and collaboration go hand-in-hand. If you want to join a team where your work shapes how our most valued clients experience both financial and lifestyle services, this is the place for you.

Here’s what we stand for:

We Are Client-Centric:Every solution starts with understanding our clients’ needs.

We Are Collaborative:We achieve more when sales, product, and operations work as one.

We Are Solution-Focused:Complex problems are opportunities to innovate.

We Are Supportive:We empower each other to deliver our best.

We Celebrate Impact:Every role matters, every client counts.