Senior AI Backend Engineer (Python/FastAPI)

Job Type: Contract

Contract Duration: 6 Months

Pay Rate: CAD $90-100/hour (depending on experience and alignment)

Location: Hybrid, 1 day onsite weekly, Downtown Toronto, ON

Your New Company

Our client is investing in next-generation AI-powered applications and is expanding its engineering team with experienced contractors who can help design, build, and scale production-grade AI solutions. This is an opportunity to work on innovative Agentic AI initiatives involving Large Language Models (LLMs), cloud-native architectures, API integrations, and contemporary AI orchestration frameworks.

Your New Role

As a Senior AI Backend Engineer, you will be responsible for designing, developing, and deploying production-grade AI applications and backend services. You will build scalable Agentic AI workflows, integrate Large Language Models, and contribute to cloud-native solutions that support enterprise-scale applications.

Working closely with engineering leadership and technical teams, you will help architect intelligent systems leveraging modern AI frameworks, retrieval systems, cloud services, and observability tooling.

Key Responsibilities

- Design and develop scalable backend services and APIs using Python and FastAPI
- Build production-grade AI applications leveraging Large Language Models (LLMs)
- Design and implement Agentic AI workflows and autonomous agent systems
- Develop and maintain Retrieval-Augmented Generation (RAG) solutions
- Integrate external and internal services through REST APIs
- Implement LLM tool calling, structured outputs, and workflow orchestration
- Build and optimize cloud-native applications utilizing GCP, AWS, or Azure
- Develop integrations with BigQuery, databases, vector stores, and enterprise systems
- Containerize and deploy applications using Docker and modern CI/CD pipelines




- Implement authentication and authorization workflows for secure services
- Collaborate with architects, product teams, and developers on technical design and solution architecture
- Maintain performance, scalability, observability, and reliability of production systems
- Participate in code reviews, architecture discussions, and technical leadership activities

What You'll Need to Succeed

Required Qualifications

- 10+ years of software engineering experience
- Strong Python development experience building production-grade applications
- Hands-on experience developing backend services using FastAPI
- Experience building and deploying scalable REST APIs
- Experience building AI-powered applications utilizing LLMs
- Experience developing Agentic AI workflows and autonomous AI systems
- Hands-on experience with LangGraph and LangChain
- Experience implementing Retrieval-Augmented Generation (RAG) architectures
- Experience integrating AI services through REST APIs
- Experience with LLM tool calling and structured outputs
- Strong experience designing cloud-native applications
- Experience with Google Cloud Platform (GCP), AWS, or Azure
- Experience integrating applications with databases and data platforms including BigQuery
- Familiarity with Redis caching strategies
- Experience with authentication and authorization workflows (OAuth, JWT, SSO, etc.)
- Experience with Docker and CI/CD pipelines
- Strong understanding of software design principles, scalability, performance optimization, and secure coding practices

Preferred Qualifications





- Experience with Langfuse or similar AI observability platforms
- Experience with vector databases and semantic search architectures
- Experience developing multi-agent systems
- Experience deploying applications on GCP using services such as BigQuery, Cloud Run, GKE, Dataflow, or Cloud Storage
- Understanding of machine learning and data science fundamentals
- Experience supporting enterprise-scale AI applications in production environments

What You'll Get in Return You will join a highly skilled engineering team working on innovative AI initiatives and modern cloud-native solutions. This engagement offers the opportunity to work with cutting-edge technologies including Large Language Models, Agentic AI architectures, LangGraph, LangChain, and GCP while contributing directly to the development of enterprise-scale intelligent systems.

Compensation is competitive and commensurate with experience, with flexibility for exceptional candidates who demonstrate strong alignment with the technical requirements.

Interview Process

Round 1

45 minutes

- Resume and project experience review
- Cultural fit assessment
- High-level technical discussion
- AI application and backend engineering experience

Round 2 60 minutes

- Technical interview with engineering leadership
- Deep dive into architecture, AI workflows, backend design, and implementation experience

What You Need to Do Now If you're interested in this role, click 'apply now' to forward an up-to-date copy of your CV, or contact us directly for a confidential discussion regarding this opportunity.

If this job isn't quite right for you, but you are looking for a new position, please contact us for a confidential discussion on your career.

This posting is for an existing vacancy with the organization.

AI may be used to screen, assess, or select applicants for the position.

📌 Senior AI Backend Engineer (Python/FastAPI) (Toronto)
🏢 Hays
📍 Toronto