Full Stack Developer

WALT Labs; Greater London; On-site; GBP 60,000 - 90,000; Full time

Job summary

WALT Labs in Greater London seeks a capable Full Stack Developer to build and ship the Companion product suite — an AI-powered automation and intelligence platform.

You will implement Companion modules, AI agents, automation workflows, MCP server integrations, and ensure production-grade code with tests and security.

Reporting to the VP of Product, you’ll deliver roadmap features and contribute to secure, scalable integrations with Salesforce, QuickBooks, Harvest, and BigQuery.

Qualifications

• 3+ years of full-stack software development with production deployments.
• Proficiency in modern frontend frameworks (React or equivalent) and backend API development.
• Experience building and integrating with APIs, webhooks, and third-party platforms.
• Solid understanding of CI/CD pipelines, version control (Git), and release management.
• Demonstrated ability to write clean, tested, maintainable code with security in mind.

Responsibilities

• Develop Companion modules across UI, API, data, and AI agent layers.
• Implement AI agents, automation workflows, and routing logic connecting to systems.
• Build and maintain MCP servers and cross-system integrations (Salesforce, QuickBooks, Harvest, BigQuery).
• Write production-grade code with tests; follow CI/CD, security, and release processes.
• Own operational health of features including monitoring, incidents, and post-deploy fixes.

Skills

Full-stack

React frontend

Backend APIs

APIs & Integrations

CI/CD & Git

Security mindset

Job description

The Full Stack Developer builds and ships the Companion product suite — the AI-powered automation and intelligence platform that runs WALT Labs. This role is responsible for the implementation of Companion modules, AI agents, automation workflows, MCP servers, and cross-system integrations across the company's operating stack. The role reports to the VP, Product and works against an established roadmap to deliver production-grade software on a fast cadence.

KEY RESPONSIBILITIES

In this role, you will:

• Companion Module Development: Build and ship features across the Companion product suite, including UI, API, data, and AI agent layers, against the roadmap defined by the VP, Product.
• AI Agents and Automation Workflows: Implement AI agents, automation workflows, and workflow routing logic that connect the Companion suite to internal and external systems.
• MCP Servers and Integrations: Build and maintain MCP servers and cross-system integrations across the operating stack, including Salesforce, QuickBooks, Harvest, BigQuery, and other production systems.
• Code Quality and Release Discipline: Write production-grade code with appropriate test coverage. Follow established CI/CD standards, security practices, and release processes across every commit and deployment.
• Operational Ownership: Own the operational health of shipped features, including monitoring, incident response, and post-deployment fixes. Surface blockers, dependencies, and risk early in the daily product sync.

QUALIFICATIONS & EXPERIENCE

Required:

• 3+ years of experience in full-stack software development with production deployments
• Proficiency in modern frontend frameworks (React or equivalent) and backend API development
• Experience building and integrating with APIs, webhooks, and third-party platforms
• Solid understanding of CI/CD pipelines, version control (Git), and release management practices
• Demonstrated ability to write clean, tested, maintainable code with strong attention to security

Preferred:

• Experience working in a Google Cloud or managed services environment
• Hands-on experience building AI agents, LLM integrations, or MCP servers
• Familiarity with Salesforce, QuickBooks, Harvest, or BigQuery integrations
• Prior experience in a fast-paced, product-led startup or scale-up environment

WHAT SUCCESS LOOKS LIKE

• In your first 30 days — you are fully onboarded, environment is set up, you understand the Companion suite architecture, and you have shipped your first production contribution.
• In your first 90 days — you are operating independently against the roadmap, your code is consistently passing review and reaching production, and you have delivered at least one complete Companion module feature.
• By the end of your first year — you are a go-to engineer on the Companion suite, actively contributing to architecture decisions, and your work is measurably reducing manual operations across the business.