Sr. Software Engineer, Fullstack (UK)
Summary
Senior full stack engineer at Firstup building and owning scalable, multi-tenant SaaS services for its employee communications platform — spanning frontend, backend, and data layers. Work emphasizes reliability and performance, shift-left testing, AI-assisted development, and mentoring, using Ruby on Rails, TypeScript, Node.js, Go, and React.
Job Summary
We're looking for a Senior Full Stack Engineer who thrives at the intersection of craft and scale. You'll design and deliver large-scale, multi-tenant cloud services — with a relentless focus on availability, fault-tolerance, and elegant architecture. You'll set the bar for engineering quality and help elevate those around you.
Responsibilities
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Core Engineering & Ownership: Build and own scalable SaaS applications end-to-end — frontend, backend, and data layers. Write production-grade code that is reliable, readable, efficient, and testable. Raise the bar through thoughtful code reviews and comprehensive documentation.
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System Architecture: Design future-ready architectures and proactively close gaps before they become problems.
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Performance & Reliability: Drive system availability and performance — investigate, analyze, and resolve reliability issues across the stack. Recognize opportunities and advocate for better performance and efficiency of software, systems, and processes across teams.
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Shift Left Testing & Quality: You champion a rigorous 'shift-left' quality culture, embedding comprehensive testing—unit, integration, and contract—early and continuously in the development lifecycle, not as an afterthought.
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AI Integration: Leverage and advocate for AI-assisted tools (e.g., GitHub Copilot, Claude) to accelerate development while maintaining rigorous engineering judgment and accountability for code correctness.
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Leadership: Drive team-wide best practices, conduct quality code reviews, and mentor engineers to elevate overall engineering quality.
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Collaboration (Product & Design): Partner with Product and Design to translate requirements into intuitive UI, making informed technical trade-offs in the face of ambiguity.
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Collaboration (Engineering Standards): Champion engineering best practices across teams and collaborate on solving complex, high-impact problems.
Minimum Qualifications
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Bachelor's degree in Computer Science or related field, or equivalent experience.
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8+ years building reliable, performant applications and microservices in production environments. Proven full stack fluency - you're comfortable across frontend, backend, and the database layer.
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A polyglot mindset — you evolve with the tech. Familiarity with Ruby on Rails, TypeScript, , Go, or React.js is a strong plus.
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Proven full-stack experience across frontend (React.js), backend, and database layers.
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Contribute to production health, including on-call rotations and incident response, in a "you build it, you run it" environment.
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Technical depth in at least one engineering domain: distributed systems, multi-tenant SaaS, application databases, networking, security, serverless, event streaming, or similar.
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A genuine drive to build beautiful, intuitive products with the customer always in focus. Innate curiosity — you love learning and have a desire to teach and lift others. Strong communication skills and openness to collaborative idea-sharing across teams.
Preferred Qualifications:
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Core Stack Experience: Familiarity with Ruby (including Ruby on Rails), TypeScript, Node.js, Go, or React.js is a strong plus.
Skills
As published by lever · 22 questions · 3 written answers
Basics
Resume/CV, Full name, Email, Phone, Current location, Current company, LinkedIn URL, GitHub URL, Stack Overflow URL, Portfolio URL, Twitter URL, Other website
Short answers (8)
- Name
- Position Applying For
- Address
- University
- Name optional
- Position Applying For optional
- Address optional
- University optional
Pick from a list (11)
- Gender
- Do you have the right to work in the UK?
- Do you now or will you in the future require sponsorship to work legally in the UK? Please note: proof of eligibility may be required at the time of hire.
- Gender optional
- Please confirm which community background you identify with: optional
- Which of the following technologies have you used professionally in a production environment? optional
- How many years of professional software engineering experience do you have? optional
- Which best describes your primary experience? optional
- Which of the following have you owned in a production environment? optional
- Do you actively use AI coding tools (e.g., Copilot, Claude, ChatGPT) in your daily workflow and validate their outputs before production use? optional
- Which testing approaches have you used in production? optional
Written answers (3)
- If your right to work in the UK is time-limited, please confirm your visa category and expiry date.
- What are your salary expectations (approx.)?
- What interests you about this role, and what type of engineering challenges are you looking for next? optional
