Firstup

Sr. Software Engineer, Fullstack (UK)

Posted 2 Days Ago

Hiring Remotely in London, Greater London, England, GBR

Remote or Hybrid

Senior level

Information Technology • Other • Software

The Role

Build and own scalable full-stack SaaS applications across frontend, backend, and database layers. Design reliable multi-tenant cloud architectures, improve availability and performance, embed unit, integration, and contract testing, and participate in on-call and incident response. Collaborate with Product and Design, conduct code reviews, document systems, promote engineering standards, use AI-assisted development tools responsibly, and mentor engineers.

Summary Generated by Built In

Who We Are

At Firstup, our mission is to improve the employee experience at every moment that matters, large and small. As the communication pipeline for the world's workforce, we now serve 40 of the Fortune 100 companies, reaching and connecting more than 17 million employees daily.

Our employees are experts in the employee experience, workforce communications and technology.

Joining Firstup means joining a movement to make work better for every worker. As the world’s first intelligent communication platform, Firstup meaningfully engages employees at every moment from hire to retire, and delivers engagement insights to help companies support, promote and retain their talent. Our movement has taken root and is evident in our world-class customer base. Now we need your help. Ready to make a difference in the world?

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

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.

System Architecture: Design future-ready architectures and proactively close gaps before they become problems.

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.

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.

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.

Leadership: Drive team-wide best practices, conduct quality code reviews, and mentor engineers to elevate overall engineering quality.

Collaboration (Product & Design): Partner with Product and Design to translate requirements into intuitive UI, making informed technical trade-offs in the face of ambiguity.

Collaboration (Engineering Standards): Champion engineering best practices across teams and collaborate on solving complex, high-impact problems.

Minimum Qualifications

Bachelor's degree in Computer Science or related field, or equivalent experience.
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.
A polyglot mindset — you evolve with the tech. Familiarity with Ruby on Rails, TypeScript, Node.js, Go, or React.js is a strong plus.
Proven full-stack experience across frontend (React.js), backend, and database layers.
Contribute to production health, including on-call rotations and incident response, in a "you build it, you run it" environment.
Technical depth in at least one engineering domain: distributed systems, multi-tenant SaaS, application databases, networking, security, serverless, event streaming, or similar.
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:

Core Stack Experience: Familiarity with Ruby (including Ruby on Rails), TypeScript, Node.js, Go, or React.js is a strong plus.

Why Firstup?

Because you care - about people, the work you do, and the connections you make. Work is such a large part of life; it only makes sense to make it awesome.

If you want to engage brilliant minds in a high-growth and inclusive environment where ideas are rewarded regardless of who they come from, join us. This is a rapidly changing space so if you thrive on ambiguity, are hungry for a challenge, and have the guts to speak your mind, you could be a perfect fit.

We offer an excellent PTO program, great health benefits, a casual and friendly environment, remote work, and a leadership team who truly believes in your growth – both personally and professionally.

Firstup is committed to providing equal employment opportunities to all applicants for employment and to all employees, without regard to race, color, religion, gender, sexual orientation, gender identity or expression, national origin, age, protected disability, veteran status, or any other protected status in accordance with applicable federal, state or local laws.

#LI-TM1

#LI-Remote

Skills Required

Bachelor's degree in Computer Science or a related field, or equivalent experience
8+ years building reliable, performant applications and microservices in production environments
Full-stack experience across frontend, backend, and database layers
Production health experience, including on-call rotations and incident response
Technical depth in at least one domain such as distributed systems, multi-tenant SaaS, application databases, networking, security, serverless, or event streaming
Strong communication and collaboration skills
Experience with Ruby, Ruby on Rails, TypeScript, Node.js, Go, or React.js

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The Company

HQ: San Francisco, CA

259 Employees

What We Do

Firstup is redefining the digital employee experience to put people first and lift companies up. We make communication solutions that build authentic engagement and create two-way conversation between employees and companies. Our powerful orchestration engine connects every worker, everywhere, on any device with personalized information that helps them do their best work. That’s why 40% of Fortune 100 companies like Amazon, ABInBev, Ford and Pfizer have chosen us to power their frontline, simplify their digital workplace and unlock the potential of their workforces.