Senior Full-Stack Engineer — Hybrid London SaaS Scale

Owen Thomas B Corp; Greater London; Hybrid; GBP 100,000 - 140,000; Full time

Benefits offered by this job

Health insurance

Flexible work hours

Job summary

Firstup in London is seeking a Senior Full Stack Software Engineer to design and deliver large-scale, multi-tenant cloud services with a focus on availability, reliability, and elegant architecture.

You will own end-to-end development across frontend, backend, and data layers, write production-grade code, and mentor engineers to elevate quality while collaborating with Product and Design.

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 experience across frontend (React.js), backend, and database layers.
• Contribute to production health, including on-call rotations and incident response.
• Technical depth in at least one domain: distributed systems, multi-tenant SaaS, databases, networking, security, serverless, or similar.
• Drive to build beautiful, intuitive products with the customer in focus; strong collaboration skills.

Responsibilities

• 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.
• Conduct thoughtful code reviews and maintain comprehensive documentation.
• Design future-ready architectures and proactively close gaps.
• Drive system availability and performance; investigate and resolve reliability issues.
• Champion shift-left testing and quality across the lifecycle.
• Leverage AI-assisted tools to accelerate development while ensuring code correctness.
• Lead by example, mentor engineers, and elevate engineering quality.
• Collaborate with Product & Design to translate requirements into intuitive UI.
• Promote engineering standards and solve high-impact problems.

Skills

Full stack fluency

React.js

TypeScript

Node.js

Go

Ruby on Rails

Education

Bachelor’s degree in Computer Science or related field

Job description

Firstup in London is seeking a Senior Full Stack Software Engineer to design and deliver large-scale, multi-tenant cloud services with a focus on availability, reliability, and elegant architecture.

You will own end-to-end development across frontend, backend, and data layers, write production-grade code, and mentor engineers to elevate quality while collaborating with Product and Design.