Senior Developer (Ruby on Rails)

Help us scale smarter, faster, and with purpose

Since 2005, we’ve helped organisations achieve their goals through simple, sustainable, and scalable information security. What started as a solution to help UK police forces share sensitive data securely has grown into a global SaaS platform — IO — trusted by thousands of businesses worldwide.

We’re growing fast. Backed by private equity investment and with customers across the UK, Europe, the US, and APAC, we’re expanding our team and doubling down on our mission: to set the standard for information security management and deliver compliance confidence through our exceptional people, process, and platform.

That’s where you come in.

About the role

We are hiring a Senior Developer (Ruby on Rails) to join our backend team.

This is a senior individual contributor role with leadership expectations. You will work closely with the Tech Lead to deliver roadmap work, improve architecture where needed, and help shape how AI is used across engineering in a practical, measurable way.

This role suits someone who is comfortable working in a mature Rails monolith, can move between legacy and modern patterns without drama, and is motivated by making a real contribution in a small, capable team.

The role is based in the UK and applicants will require independent right to live and work in the UK.

What you’ll be doing

• Build and maintain product features in Ruby on Rails
• Contribute to architecture decisions and help evolve the platform over time
• Work across legacy and modern parts of the application with confidence
• Improve performance, maintainability and developer productivity
• Support the team with code review, pairing, technical planning and mentoring
• Help define and improve AI-augmented engineering workflows
• Contribute ideas, not just delivery

Our stack

Our core application is a long-running Rails monolith with over 15 years of history. That means some older patterns still exist, but new development is moving in a clear modern direction.

Current stack:

• Rails 8.1
• Ruby 4.x
• MySQL 8.x
• GitHub Actions
• Cypress end-to-end testing
• Turbo
• Literal::Types
• StimulusJS
• Service Objects moving toward dry-rb libraries
• Action Policy
• RailsEventStore::Event
• DelayJob
• New Relic
• JIRA
• Confluence

In transition / strategic direction:

• ERB moving toward Phlex
• Solr moving toward ElasticSearch / OpenSearch
• Redis potentially moving toward Solid Cache
• Component separation as a strategic step toward Packwerk

What you bring

AI and Engineering at IO — We are serious about using AI to improve speed, quality and leverage across engineering. This is not a nice-to-have for us.

We want someone who already uses AI heavily in day-to-day engineering work, passionate about it and understands its strengths and limits, and can help us build better workflows around it.

That includes practical use of tools such as OpenAI Codex, Claude Code and GitHub Copilot.

We are looking for pragmatic AI proficiency, not buzzwords. That means using AI well for delivery, refactoring, testing, documentation, automation and developer productivity, while keeping engineering judgement firmly switched on.

Must-haves

• 5+ years of relevant Ruby on Rails experience
• Strong Ruby fundamentals and sound object-oriented design skills
• Strong backend engineering capability, with working knowledge of frontend concepts
• Experience working effectively in a mature monolith
• Strong SQL skills and confidence writing and understanding queries
• Experience testing Rails applications across unit, integration and end-to-end levels
• Experience contributing to architecture and technical direction
• Strong written and verbal communication
• High autonomy, initiative and product awareness
• Daily, practical use of AI engineering tools
• Confidence using AI for coding, refactoring, testing, documentation and workflow improvement
• Good judgement about where AI helps and where it does not

Nice to haves

• Experience with Stimulus, Turbo or Hotwire
• Experience with event-driven architecture
• Familiarity with security and compliance domains
• Familiarity with ISO 27001 or similar standards
• Experience with agentic workflows, automation design or evals
• Personal projects demonstrating thoughtful AI use

Why you’ll love it here

We are a small engineering organisation, so this role has real scope and real responsibility. We value people who can contribute beyond the ticket in front of them, collaborate well, and help improve how the team works.

We already have strong processes in place:

• Backlog Review
• Product Workshops
• Technical Workshops
• JIRA Tickets -> Sprint Planning
• Sprints Demo
• Feature Retro