Senior .Net Developer

We’re looking for a senior developer to design and build backend services for our investment technology platform, supporting portfolio management, financial analytics, reporting and integrations. This is a hands-on engineering role with ownership from design through to production.

You’ll work closely with product stakeholders and other engineers, contribute to architectural decisions and build software with reliability, security and maintainability at its core.

This is an exciting time to join as we continue to invest in and develop our technology offering following the acquisition of AI-driven investment manager Collidr.

What does the role entail

• Own backend features and services throughout their lifecycle, from shaping requirements and designing solutions to implementation, testing, deployment and production support.
• Design and develop REST and GraphQL APIs, background processing and integrations using C#, .NET and ASP.NET Core.
• Build reliable asynchronous workflows, accounting for message delivery, retries, idempotency and data consistency.
• Design and develop relational data models and data access patterns with performance, scalability and efficient resource use in mind.
• Design API contracts and database schema changes with backwards compatibility and safe deployment in mind.
• Build automated testing, structured logging, metrics and tracing into services to support reliable delivery and visibility into production behaviour.
• Make well-reasoned technical decisions that meet business requirements and uphold high standards of reliability, security, performance and maintainability.
• Contribute to code reviews, share knowledge and mentor other developers.

What we’re looking for

• Strong C# and .NET experience: You have built and maintained production applications using ASP.NET Core, including designing and developing REST and GraphQL APIs.
• A solid understanding of asynchronous programming, multithreading and concurrency: You can write efficient, thread-safe code and reason about shared state, cancellation, synchronisation and resource management.
• Experience with asynchronous messaging: You understand message delivery guarantees, retries, idempotency and error handling.
• Strong relational database fundamentals: You have worked with PostgreSQL, Microsoft SQL Server or similar databases and are comfortable with SQL, schema design, indexing, transactions and query performance.
• Experience with Docker and cloud environments: You understand how backend applications are packaged, configured, deployed and supported on a cloud platform such as AWS or Azure.
• Strong software engineering practices: You write clean, maintainable code and consistently apply principles including KISS, DRY and SOLID, alongside defensive programming, meaningful validation and robust error handling.
• Good testing and observability practices: You write useful unit and integration tests and use structured logging, metrics and distributed tracing to understand application behaviour and support production services.
• An understanding of application security: You design services with authentication, authorisation and secure handling of sensitive data in mind.
• Experience with version control systems such as Git: You are comfortable with branching, pull requests and collaborative code review.
• Ownership and clear communication: You can translate business requirements into well-designed technical solutions, explain trade-offs and work effectively with technical and non-technical colleagues.

Desirable experience

• Strong familiarity with AWS and Kubernetes.
• Experience with Helm and infrastructure as code tooling such as Terraform.
• Experience designing or working with modular monoliths and distributed systems.
• Experience building financial systems, investment platforms or related applications.
• Familiarity with Linux environments.
• Experience with CI/CD pipelines and automated deployment processes.
• Experience with caching strategies, including cache invalidation and consistency.

Why Join Isio

Isio is a fast-growing professional services business, that offers career development through an evolving client base, diverse and meaningful work, nationwide opportunities, and a culture that rewards high performance and accountability.

We hold ourselves to the highest standards and our values guide how we advise our clients, how we operate as a business and how we work together as a team. We call it the Isio Attitude. We encourage our people to be bold, to communicate with conviction, and to deliver advice that matters.

Here, growth brings opportunity - more responsibility, more clients, and work that stretches and develops you. We invest in training and development so you can expand your skills and explore different career paths across diverse markets to make your mark. Isio is a place to realise your potential and build a career with impact. You can find out more about Isio and the benefits we offer on our career's websiteIsio - Careers & Benefits.

About Isio

A progressive advisory firm, partnering with clients of all sizes to deliver expertise in pensions, employee benefits and wealth advisory services.

Working with pension trustees, employers, individuals, families and their offices, we are supported by talented colleagues across 10 UK offices. With a Big 4 heritage we combine a strong focus on quality with a fresh perspective challenging traditional thinking.

Our culture shapes our work; we foster a supportive environment where we develop our people to grow and fulfil their potential. We invest in our services, products and technology, and provide clear, expert solutions for our clients. This brings clarity, confidence, and better outcomes for everyone.

At Isio, we are committed to fostering an inclusive, equitable and diverse workplace, in which our colleagues feel they belong, regardless of background or difference. We uphold the values of respect, fairness, and inclusion in our actions and decisions. We believe that by adhering to these principles, we will create a stronger, more innovative, and supportive environment for all, as well as ensuring that the advice and support we provide to our clients is more creative, more insightful and leaves a lasting impact.

We can offer a hybrid, flexible approach to work, supporting a work-life balance that works for you. Isio Group is an equal opportunities employer, and we welcome applications from all suitably qualified candidates.

If you think you may require a reasonable adjustment to be made for any reason at any stage of your recruitment process, please ask us hrrecruitment@ISIO.com