Senior Full Stack Engineer

Senior FullStack Engineer AI-Centric | Spec-Driven | Agent-First Development Location: Remote (Canada) Engagement Type: B2B contractor About Revenue Roll We're looking for a Senior FullStack Engineer with strong AI and agentic development experience to join our growing team. You'll lead the development of user interfaces and services that power marketing analytics, identity resolution, and cross-platform personalization — leveraging AI agents and spec-driven workflows to ship faster and smarter. What You'll Do Build and maintain high-performance, scalable web applications using Node.js, React.js, GCP, MongoDB. Develop features end-to-end using AI-assisted, spec-driven workflows — creating detailed technical specifications and implementing them via AI coding agents (Claude Code, Codex, Gemini CLI). Work closely with Data Scientists, GTM Engineers and Backend Engineers to bring graph- based identity resolution, campaign analytics, and data activation to life. Design UIs with advanced data visualization (e.g., using Highcharts, Recharts, etc.). Collaborate on multi-tenant architecture, OAuth-based integrations, and automated onboarding experiences using Auth0, Firebase, and Google Cloud Functions. Work with the backend team to integrate features and deliver end-to-end value, including billing, Slack alerting, email messaging and integration with various third-party services. Drive test automation using Vitest and Jest, and help ensure performance monitoring with OpenTelemetry and Sumo Logic. Define and refine AI agent configurations — custom instructions (CLAUDE.md), hooks, skills, and prompt templates — to optimize team-wide development workflows. Build and maintain MCP Servers to expose internal REST/HTTP APIs to AI agents, enabling seamless tool-use across the development lifecycle. Champion UI/UX best practices while maintaining clean, maintainable code using ESLint, Prettier, SonarQube, etc. Act as a Feature Lead, leading the architecture, technical documentation, communication with CTO, Tech Lead and Product Owner on the best tech realization of the selected feature. Must-Have Qualifications By experience, we mean experience in commercial software development. 7+ years experience (commercial!) with JavaScript/TypeScript and modern frameworks. 7+ years experience with Node.js 20+, Express.js 4+, (or Nest 10+), and related tooling. 5+ years experience with React.js, including hooks and context API. Extensive experience with document-oriented databases, specifically MongoDB. Proven experience with AI-assisted development using tools like Claude Code, Codex, or Gemini CLI to accelerate coding, debugging, and code review. Experience with prompt engineering and LLM API integration (Anthropic, OpenAI, Google, open-source LLMs). Ability to author and interpret detailed technical specifications for front-end and back-end features, enabling efficient AI-driven development. Experience with Serverless environments, especially Google Cloud Platform: Cloud Run/Functions, App Engine, Firebase, Logging, API Gateway. Deep understanding of REST APIs. Strong experience building CI/CD workflows using GitHub Actions. Strong drive to build products through AI agents rather than manual coding. English proficiency at intermediate level or higher. Bonus Points Experience with Neo4j and graph data modeling (e.g., identity graphs). Familiarity with BigQuery and CDP tools. Experience with low-code/no-code solutions such as n8n, Zapier, and Node-RED. Experience building dashboards for analytics or marketing tech platforms. Hands-on experience building or integrating agentic AI workflows (e.g., LLM-powered pipelines, tool-use agents, RAG systems). Familiarity with prompt engineering and LLM API integration (Anthropic, OpenAI, Google). Experience creating custom skills/plugins for AI agents and building MCP Servers on top of existing REST/HTTP APIs. Ability to use Claude Code (or similar tools) beyond code generation — for technical documentation, DevOps troubleshooting, and CI/CD pipeline configuration. Tech Stack You'll Work With Frontend: Web APIs, React, Vite, Tailwind. Backend: Node.js, Express, Nest, MongoDB, BigQuery, Auth0, Google APIs, GitHub APIs, third-party APIs. AI Development: Claude Code, Codex, Gemini CLI, MCP Servers, spec-driven development workflows. DevOps/Tooling: GitHub Actions/Workflows, NX, Turborepo, Prettier, ESLint, npm, pnpm, Vitest, Jest and such.