Senior Full Stack Developer – AI Outbound Sales Custom Agent

Overview

The Senior Full Stack Developer is a hands-on role within our client’s AI team, focused on building the core systems that power an AI-driven Custom Agent and integrated Light CRM platform. This role is critical to the development of a fast-moving, mission-critical MVP, ensuring that frontend, backend, integrations, and platform workflows come together in a scalable, reliable, and production-ready environment.

You will work across a cross-functional team that includes AI/ML Engineering, Telephony, DevOps, QA, and Full Stack development. Reporting to the Team Leader, you will play a central role in translating product and technical requirements into working systems, helping architect and deliver the platform from the ground up.

Success in this role requires strong full stack development capability, technical fluency across modern web and backend systems, experience with real-time and integrated platforms, and the ability to work effectively in a complex, fast-evolving environment.

Job Description – Senior Full Stack Developer – AI Digital PlatformPosition Overview

Our client is building a next-generation AI Digital Platform that combines voice-enabled conversational AI, telephony integration, and a lightweight CRM into one seamless system. This is a high-impact, hands-on role where you’ll help architect and build production-grade systems that span AI, real-time telephony, and modern SaaS web applications.

Role Overview

As a Senior Full-Stack Developer, you will take ownership of critical components across the stack — from the CRM frontend/backend to the AI management orchestration system and its integrations. You will collaborate closely with AI/ML engineers, who focus on STT, LLM, and TTS models, as well as the infrastructure team, ensuring that data, APIs, and workflows are robust, scalable, and reliable.

You will thrive if you enjoy working in high-performance, real-time systems and have experience bridging frontend usability with backend orchestration.

Key ResponsibilitiesBackend & API Development

* Build and maintain FastAPI/Node.js services powering the AI Management System, including call orchestration, dialogue state, and outcome extraction.

* Design clean REST APIs and Webhooks for CRM, telephony, and automation integrations (e.g., n8n).

* Implement robust data models in PostgreSQL and caching/queuing via Redis.

Frontend & CRM Development

* Lead development of the CRM operator console using React/Next.js.

* Create dashboards for lead management, call outcomes, and campaign analytics.

* Ensure intuitive UI/UX for sales teams monitoring AI calls.

Systems Integration

* Integrate backend services with telephony platforms such as Asterisk, FreeSWITCH, SignalWire, and Twilio.

* Connect AI pipeline outputs (STT, LLM, TTS) to CRM outcomes.

* Implement flexible adapters for direct CRM API connections and workflow automation via n8n.

Scalability & Observability

* Optimize system performance for high-volume concurrent calls.

* Implement monitoring, logging, and alerting with Prometheus, Grafana, and Sentry.

* Ensure fault tolerance and horizontal scalability of orchestration and web services.

Collaboration & Leadership

* Work closely with AI developers to ensure seamless integration.

* Participate in architectural reviews, code reviews, and mentoring junior developers.

* Contribute to the technical roadmap and best practices for CI/CD, testing, and security.

Key Qualifications – Must Have

* 7+ years of full-stack development experience.

* Strong expertise in Python and/or Node.js, including FastAPI.

* Proficiency in React/Next.js for frontend web applications.

* Solid experience with PostgreSQL and Redis (queues, caching, pub/sub messaging such as Kafka or RabbitMQ).

* Proven ability to design, build, and scale REST APIs and distributed systems.

* Familiarity with telephony stacks such as Asterisk, FreeSWITCH, SignalWire, or Twilio.

* Experience integrating external SaaS APIs, including CRMs and automation tools.

* Experience supporting custom AI agent development (RAG architectures, prompt/context orchestration, memory frameworks).

* Experience evaluating and improving LLM outputs (prompt iteration, response quality assessment, basic evaluation frameworks).

Nice to Have

* Experience deploying and running open-weight LLMs (e.g., LLaMA) locally using tools like vLLM, Ollama, or similar.

* Familiarity with lightweight fine-tuning techniques (LoRA / QLoRA) and tools like Hugging Face Transformers / PEFT.

* Prior experience building high-throughput sales or communications platforms.

* Familiarity with feature flagging, A/B testing, and experimentation frameworks.

* Understanding of DevOps in cloud environments such as AWS or Azure; Docker and Kubernetes are a plus.

Closing Profile

This role is for someone who thrives in building complex systems end-to-end, enjoys solving real-time, distributed challenges, and wants to see their work directly power a live AI sales platform.

Location: Toronto Office (Hybrid)

Reporting To: Team Leader

Status: Contract