Senior Fullstack Software Engineer Firstup

Abundant Code; Greater London; Hybrid; GBP 110,000 - 150,000; Full time

Benefits offered by this job

PTO program

Health benefits

Remote work

Job summary

Firstup is seeking a Senior Full Stack Engineer to design and deliver large-scale, multi-tenant cloud services with a relentless focus on availability and elegant architecture. You will own features end-to-end across the frontend, backend, and data layers while mentoring peers and elevating engineering quality.

You’ll champion shift-left testing, integrate AI-assisted tooling, and collaborate closely with Product and Design to translate requirements into intuitive user interfaces.

Qualifications

• Bachelor’s degree in Computer Science or related field, or equivalent experience.
• 8+ years building reliable, performant applications and microservices in production environments.
• Full-stack fluency across frontend, backend, and database layers.
• 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, and strong communication across teams.

Responsibilities

• Core Engineering & Ownership: Build and own scalable SaaS applications end-to-end – frontend, backend, and data layers.
• System Architecture: Design future-ready architectures and proactively close gaps before they become problems.
• Performance & Reliability: Drive system availability and performance across the stack.
• Shift Left Testing & Quality: Champion a rigorous shift-left quality culture with unit, integration, and contract testing.
• AI Integration: Leverage AI-assisted tools to accelerate development while ensuring code quality.
• Leadership: Drive best practices and mentor engineers to improve overall quality.
• Collaboration (Product & Design): Translate requirements into intuitive UI with informed technical trade-offs.
• Collaboration (Engineering Standards): Promote engineering standards across teams.

Skills

React.js

Node.js

Go

TypeScript

Ruby on Rails

Distributed systems

Education

Bachelor’s degree in Computer Science or related field

Tools

GitHub Copilot

Git

Job description

Senior Fullstack Software Engineer Overview

Company Name: Firstup

Job Role: Senior Fullstack Software Engineer

Qualifications: Not specified

Category: I

Job Type: Full Time

Location: Hybrid- London, UK

What we're looking for

• 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.

• 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.

Nice to have

• A polyglot mindset — you evolve with the tech. Familiarity with Ruby on Rails, TypeScript, Node.js , Go, or React.js is a strong plus.

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

The role

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.

What you'll do

• 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.

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.

Visa sponsorship: check with employer