Senior Node.js Developer UK - Flosum

Who We Are

Flosum is a bootstrapped, profitable B2B SaaS company building the leading Salesforce-native DevSecOps, Data Protection, and Security platform. Our solutions are trusted by Fortune 500 enterprises in the most heavily regulated industries on the planet — financial services, healthcare, government, and insurance.

We’re not a startup burning cash and chasing vanity metrics. We’re a proven, scaling business that reached profitability on our own terms. As a Salesforce Summit Partner and Innovation Award winner, we’ve earned our seat at the table alongside the biggest names in enterprise software.

Built 100% on the Salesforce platform. Serving enterprises that demand zero compromise on security, compliance, and reliability.

Why This Role Exists

We are entering an aggressive growth phase — expanding our product surface, deepening our platform capabilities, and accelerating our delivery velocity. We need senior-caliber Node.js developers who can own significant parts of our architecture and ship production code that enterprise customers depend on daily.

This is not a staff augmentation seat. You will work directly with engineering leadership, product managers, and the CEO. Your decisions will have real consequences, your opinions will be heard, and your craftsmanship will be visible to the customers who rely on our platform.

What You’ll Build

• High-performance backend services and APIs powering enterprise-grade SaaS applications
• Scalable, secure Node.js micro services and integrations within the Salesforce ecosystem
• Modern front-end experiences using Vue.js and TypeScript that serve demanding enterprise users
• CI/CD pipeline tooling, automation frameworks, and developer productivity infrastructure
• Real-time data processing and event-driven architectures handling sensitive enterprise data at scale

Requirements

Read this section carefully. We are specific about what we need because we are serious about who we hire.

Non-Negotiable Technical Requirements

• 5+ years of professional Node.js development in production environments — not tutorials, not side projects, not bootcamp exercises. Real production systems serving real users at scale.
• Expert-level understanding of asynchronous programming, event loops, streams, and the Node.js runtime. You should be able to explain backpressure, the differences between setImmediate and process.nextTick, and why unhandled promise rejections are dangerous — without Googling it.
• Deep experience with TypeScript in production codebases. We write typed code, and we expect you to understand why.
• Strong command of RESTful API design, authentication patterns (OAuth 2.0, JWT), and API security best practices for enterprise environments.
• Proven experience with SQL and NoSQL databases, query