Senior Full Stack Developer, Contract (4)

Role

Senior Full Stack Developer (contract) responsible for architecting, developing, and deploying web applications and cloud infrastructure using React and Node.js, with a particular emphasis on enabling agentic workflows and reliable LLM integrations.

Key Responsibilities

Core Engineering

• Optimize website performance for fast load times and efficient delivery.
• Develop and maintain APIs and ensure end-to-end integration between frontend and backend systems.
• Design and build scalable cloud infrastructure to host applications and agent operations.
• Apply security best practices to services and infrastructure.

AI Engineering

• Build and maintain automated evaluation pipelines (evals) for agent and skill outputs, including LLM-as-judge scoring, regression test suites, and golden dataset validation.
• Define strict input/output contracts for tools and agent skills using typed schemas (TypeScript interfaces, JSON Schema) and handle structured error cases.
• Own prompt engineering for assigned tools and skills: version-controlled prompt templates, parametric input injection, and system/user role separation.
• Implement, test, and document MCP-compatible API integrations (notably GraphQL/Apollo) and contribute to rollout readiness (SLOs, support docs).

Requirements

• Must be available to collaborate in the Toronto office.
• 5+ years working with modern frameworks and languages (React & Node.js).
• Familiarity with OAuth2/OIDC, API key management, and access audit trail patterns.
• Experience with Next.js or Nuxt.js server-side rendering applications.
• Experience with GraphQL and Apollo; building or integrating REST/GraphQL APIs with attention to interface contracts and versioning.
• Familiarity with SLO definition and observability practices (logs, metrics, distributed traces).
• Hands-on experience with LLM structured output patterns (function/tool calling).
• Familiarity with LLM evaluation approaches (golden test sets, LLM-as-judge pipelines, prompt regression testing) and ability to quantify output quality.
• Experience building or consuming agentic workflows (multi-step tool chains, state machine agents, or orchestration frameworks such as LangGraph, LangChain, AutoGen, or custom).

Nice to Have

• Experience defining and rolling out engineering standards across teams.
• Experience managing and growing engineers (performance conversations, career development).
• Track record driving AI tool adoption and creating onboarding/guidance for teams.
• Experience with AWS and Docker.
• Experience with Styled Components.
• Experience with prompt caching, semantic routing, or output memorization strategies.
• Ability to instrument LLM calls with structured traces using frameworks like LangSmith or OpenTelemetry and define SLOs for agent task success.

Logistics

• Contract role until December 24, 2026.
• Hybrid work model; expected to be in the Toronto office up to 2 days per week.