Senior Software Engineer

We're on a mission to protect society from fraud and money laundering. We've already protected over 3 million people through life's big transactions. Fraud and regulation are rising, costing the UK economy over £100bn every year; this makes it more difficult for businesses to protect themselves and their clients - individuals like you and me - from fraud and money laundering. About the role: You'll join Thirdfort at an exciting moment for Tenant Referencing. We're rebuilding the product from the ground up, moving it off a legacy platform onto Thirdfort's strategic engineering platform (Go, Temporal-based workflows, cloud-native). You'll be one of the first permanent engineers on a newly-formed squad, with real scope to shape how tenant referencing gets architected and make technical calls on a live migration. It matters beyond the tech, too. Tenant referencing is where our fraud-prevention mission meets something that matters to people directly: renting a home. We're looking for someone who takes ownership, is comfortable without a fully mature spec, and is pragmatic about tooling, including using AI where it helps them move faster. For this role, we would love this person to be able to join us in our London office two times a week as being together as a team is valuable for us but ultimately, we trust our team to decide what works best for them. You will achieve your mission as our Senior Software Engineer by:

• Helping lead the rebuild of our tenant referencing product, migrating it from our legacy platform onto Thirdfort's strategic engineering platform (Go, Temporal-based workflows), working across both systems during the transition
• Designing and building backend services and APIs that power tenant referencing checks, and contributing to our frontend (React/TypeScript) and mobile platforms when needed
• Making independent architecture and delivery decisions on a fast-moving, still-forming squad, working closely with our Product&Tech Lead
• Upholding engineering quality through testing, observability, and code review, as we build permanent engineering ownership into the team
• Partnering closely with Ops and Support to understand real tenant referencing workflows and translating that understanding into good technical decisions
• Using modern engineering practices, including AI-assisted development, to build new check types and features quickly without sacrificing quality
• Mentoring and uplifting engineering practices across the squad as it grows You may be right for this role if you: Hard requirements:
• Have strong backend service experience in a modern programming language, with the ability to ramp up quickly in Go
• Have experience designing, building, and integrating APIs
• Have experience working in cloud environments (AWS and/or GCP)
• Have taken ownership of ambiguous technical problems and seen them through with minimal oversight Nice to haves:
• Have experience with workflow orchestration or event-driven systems (e.g. Temporal)
• Are comfortable using AI coding tools (e.g. Copilot, Cursor, Claude Code) as part of your everyday workflow
• Have experience working across a legacy-to-modern platform migration
• Have some experience with React/TypeScript and/or mobile development