Senior Software Engineer - US

IRIS Software Group is one of the UK's largest privately held software companies, trusted by 100,000+ businesses, schools and accountancy firms to keep their operations running. Our software pays 1 in 6 UK employees, supports over 12,000 schools, and is relied on by 91 of the top 100 UK accountancy firms.

We're a Great Place to Work® certified employer, recognised for our commitment to well-being, inclusion and development - and we're growing fast.

This is a hands-on senior engineering role where you’ll solve complex problems, build scalable cloud-based software and have genuine influence over how we design and deliver our products. You’ll work across modern .NET, C#, cloud and web technologies, helping us create secure, reliable software capable of supporting large numbers of users.

We’re also evolving how we build software. As IRIS continues its journey towards becoming an AI-first organisation, you’ll have opportunities to use AI-assisted engineering tools, contribute to modern cloud architecture and help shape engineering practices across the team.

You won’t have direct reports, but you will have real technical influence. You’ll mentor other engineers, contribute to architectural decisions and help raise the engineering bar around you.

What will you be doing?

As a Senior Software Engineer, you’ll take ownership of significant areas of our products from initial design through to production.

You’ll:

• Design and deliver complex, scalable systems, including high-traffic APIs, multi-service integrations and data-processing solutions.

• Own large features and components end-to-end, from technical design and development through to deployment and production support.

• Build modern applications using C#, .NET Core, ASP.NET Core Web APIs and contemporary frontend technologies.

• Influence architecture and technology decisions, helping the team choose solutions that balance scalability, maintainability and business needs.

• Build and improve cloud-native solutions across Azure or AWS.

• Champion strong engineering practices including automated testing, TDD/BDD, CI/CD, observability, security and Infrastructure as Code.

• Work closely with Product, QA, Design, DevOps and other Engineering teams to turn requirements into high-quality software.

• Lead technical discussions, story refinement and technical problem-solving.

• Identify opportunities to reduce technical debt and improve existing systems.

• Troubleshoot complex production and performance issues.

• Mentor junior and mid-level engineers, sharing knowledge and helping others develop technically.

• Help the team use AI-assisted engineering tools responsibly and effectively to improve quality, productivity and decision-making.

What are we looking for?

We’re looking for an experienced engineer who combines strong hands-on development skills with the ability to take technical ownership and positively influence those around them.

Key technical experience:

• 5 to 7 years of professional software development experience.

• Strong backend development experience using .NET Core, C#, ASP.NET Core Web APIs and REST.

• Experience working with application architectures and distributed systems.

• Strong knowledge of SQL, NoSQL and data architecture.

• Experience with modern frontend frameworks such as Angular, React, Vue.js or Blazor, or working knowledge of frontend development alongside deeper backend expertise.

• Strong Azure or AWS experience within SaaS environments.

• Experience with cloud technologies such as Azure Functions, Queues, Blob Storage and VMs, or AWS equivalents including Lambda, SQS/SNS and EC2.

• Experience with Docker and/or Kubernetes, ideally including production-scale deployments using AKS or EKS.

• Experience with Infrastructure as Code, using tools such as Terraform, Bicep, ARM Templates, AWS CloudFormation or CDK.

• Strong understanding of CI/CD, deployment strategies and engineering automation.

• Experience with automated testing and TDD/BDD practices.

• Understanding of clean architecture, SOLID principles and domain-driven design.

• Experience building highly scalable, internet-facing software.

• Strong production troubleshooting skills, including application profiling, benchmarking and performance optimisation.

• Knowledge of observability platforms such as DataDog, Application Insights or Amazon CloudWatch.

• Good understanding of application security, vulnerability management and threat modelling.

• AI-assisted engineering

This isn’t simply about years of coding experience.

We’re looking for someone who can demonstrate:

• Ownership of complex, multi-system solutions.

• Experience working on scalable, internet-facing products.

• Technical leadership through architecture decisions, mentoring and collaboration.

• The confidence to challenge and influence technical decisions constructively.

• A track record of improving engineering standards and practices.

• Experience mentoring junior and mid-level engineers.

• The ability to lead technical initiatives spanning multiple sprints or quarters.

• Strong communication skills, including explaining technical decisions to non-technical colleagues.

• You don’t need formal management experience. We’re looking for someone who can lead through technical expertise and influence while remaining genuinely hands-on.

You don’t need everything below, but experience in any of these areas would be valuable:

• Working in regulated or complex environments such as finance, health or government technology.

• Using prompt engineering and Model Context Protocol (MCP) to connect AI systems with tools and services.

• Advanced DataDog/APM, dashboards and alerting.

• Modern UI architecture such as micro-frontends, SSR or SSG.

• Security technologies and standards including OAuth2, OIDC and RBAC.

• Event-driven architectures.

• GraphQL, SignalR or WebSockets.

• DevOps automation and true end-to-end ownership of software in production.

• Advanced Azure or AWS certifications.

• Impact: Your work will influence millions globally.

• Growth: Continuous learning and career development opportunities.

• Belonging: A culture that celebrates diversity and empowers every individual.
  

Click Apply - we’re excited to learn about your unique perspective and experience. If you need adjustments during the process, let us know. We’re committed to making this opportunity accessible to everyone.

Our process is designed to be fair, transparent and straightforward. Stages vary depending on the role — more senior positions may involve additional steps, and some areas include role-specific assessments such as a technical test or case study — but typically you can expect:

1. Application review — we assess your experience and potential

2. Initial call — a short conversation to learn about you and share more about the role

3. Skills assessment — tailored to the position, e.g. case study, coding challenge or portfolio review

4. Final interview — meet the team and explore how you'll make an IMPACT at IRIS

We'll always walk you through the specific stages at the start of the process so you can prepare with confidence.

If you need any adjustments or accommodations during the process, let us know, we’re committed to making this experience accessible for everyone.