We are hiring a senior backend engineer to take ownership of the backend across two AI-native products.Platypus is a consulting platform with an NBED multi-agent AI assistant. Quarus is a multi-tenant 3D data visualization platform with an in-app AI analyst. Python/Fast API Async SQL Alchemy on Postgres SQL Redis Back Server Send Event for real-time updates Cloud-based agent system built on PyTantic AI Quarus, add a Polyglot dimension, a Go Compute service behind Connect RPC protobuf and a temporal orchestrated data pipeline.

You'll be an end senior IC on a small fast-moving team where AI coding agent, Claude code, and autonomous agent committer are part of the daily workflow. You'll direct them, review their output, and help evolve how we use them. Own backend architecture, delivery, and operations across both products — from API design through database schema, migrations, and production deployment.

Design and extend LLM agent systems: tool-calling agents, agent routing and handoff, conversation memory and summarization, RAG pipelines, and structured-output classification.

Keep AI features safe and economical: prompt-injection hardening, per-tenant ownership guards in agent tools, token/cost accounting, and rate limits that bound paid-call fan-out. Auth0 (JWT/JWKS, Organizations), role- and scope-based access control, and tenant-isolation correctness (including IDOR prevention).

Own durable data pipelines: Docker-based environments, Kubernetes (Kustomize) and droplet deployments on DigitalOcean, Terraform, GitHub Actions CI/CD, and SOPS-encrypted secrets.

Uphold a strong quality bar: extensive pytest suites (unit + integration, high coverage thresholds), strict typing (mypy), ruff, and documentation kept current alongside the code.

Languages: Python 3.11+ (primary), Go (compute service), TypeScript (shared contracts; frontend collaboration) Frameworks: FastAPI, SQLAlchemy 2.0 (async) + asyncpg, Alembic, Pydantic v2, Pydantic AI AI/LLM: Anthropic Claude (Sonnet + Haiku),



tool-calling agents, RAG with pgvector and OpenAI embeddings, prompt engineering, token-cost auditing 7+ years of backend engineering experience, with at least 3 years building production Python services (FastAPI or similar async frameworks; Hands-on experience building LLM-powered product features — not just calling an API, but designing agent systems: tool calling, multi-agent orchestration or routing, conversation memory, structured outputs, and evaluation of model behavior. ~ Daily fluency with AI development tools — Claude Code, Cursor, Copilot, or similar. You should be comfortable directing coding agents, reviewing their output critically, and working in a codebase where agents are first-class contributors (CLAUDE.Strong relational database skills: schema design, migrations, query performance, and PostgreSQL specifics (JSONB, indexing;

Experience designing and operating multi-tenant SaaS: tenant isolation, RBAC, JWT-based auth (Auth0, Okta, or similar). ~ Production DevOps ownership: Docker, Kubernetes, CI/CD pipelines, infrastructure-as-code, and comfort being on the hook for what you ship. ~ SSE or WebSockets, pub/sub fan-out, optimistic UI reconciliation, concurrency-secure state updates.

LLM security awareness: prompt-injection defenses, cost-DoS bounds, sanitizing untrusted data at the model boundary.

Experience on small teams or early-stage products where you've owned whole systems end to end. Familiarity with report generation (PDF/DOCX), document processing, or data-ingestion pipelines. Small senior team, high trust, high ownership — you'll ship to production in your first weeks.

AI-augmented by default: coding agents open PRs, CI runs agents, and every package carries agent-facing documentation. Quality is non-negotiable: strict typing, high test coverage, conventional commits, signed commits, squash-merge, and docs updated in the same PR as the code.

Everything is reproducible: encrypted secrets in the repo, one-command local environments, infrastructure in code.

📌 Senior Backend Developer (C#, .net) (Montreal)
🏢 Plum Solutions Group
📍 Montreal