Senior Full Stack Engineer, Gen AI

About the role

Join Optibus' GenAI team to build and extend the AI assistant embedded across our product suite. The platform is a production LLM agent system that's integrated into multiple host applications, backed by a RAG knowledge base and an evaluation-driven development workflow.

You'll work end-to-end: agent design, tool implementation, retrieval quality, integration into existing product UIs, cloud infrastructure, and evaluation/observability. The platform already ships to customers — you'll extend it, raise its quality bar, and help define where it goes next.

What you'll do

• Design and evolve agents - build LLM agents with tool use, routing, and human-in-the-loop flows.
• Implement tools and integrations - expose product capabilities to the agent, with multi-tenant context, via internal APIs and MCP servers.
• Own retrieval quality - contribute to our RAG pipeline end-to-end: ingestion, embeddings, vector search, and reranking.
• Define and evolve host integration contracts - collaborate with host application teams to integrate the assistant into product UIs built on different frontend stacks. You own the shared remote module and the integration API; host teams own their stacks.
• Drive evaluation-led development - write evaluators (rule-based, LLM-as-judge, multi-turn), maintain CI eval gates, and use traces and feedback to debug production behavior.
• Operate the platform - own deployments, observability, and the performance and cost of LLM-backed services.
• Establish engineering practices** for AI-specific work: prompt versioning, eval coverage, testing, and code review.

• 7+ years of professional software engineering experience.
• Strong TypeScript — the primary language across our backend, frontend, and agent code.
• Proficiency in modern UI frameworks like React, Angular, or Vue, combined with a strong understanding of JavaScript.
• A minimum of 3 years of production experience in backend development using Node.js.
• Production experience with LLM-based applications, including prompt engineering, agent/tool-calling design, and RAG.
• Hands-on experience with an agent framework (e.g., LangGraph, LangChain).
• Vector databases and semantic search with embedding-based retrieval.
• Cloud experience on AWS — compute, storage, IAM, and managed LLM services (e.g., Bedrock or equivalent).
• Solid web fundamentals — REST APIs, WebSockets, auth (token/OIDC), and modern React.
• Docker and standard CI/CD practices.

Strongly preferred

• Python for data and ingestion pipelines.
• MCP (Model Context Protocol) — building servers, clients, or tooling.
• LLM observability and evaluation platforms (e.g., LangSmith).
• Module Federation or other micro-frontend integration patterns.
• Experience designing APIs or SDKs consumed by multiple client teams across different tech stacks.
• Infrastructure as code (AWS CDK and/or Pulumi).
• B2B SaaS background with multi-tenant context.
• Interest in the public-transit domain.

About Optibus:

Optibus is a unified software platform revolutionizing public transportation planning, scheduling, and operations in over 8,000 cities worldwide. Using AI, ML, and optimization algorithms, it empowers agencies to design more efficient, equitable, and sustainable transit networks, enhancing passenger access, reducing emissions, and improving driver conditions. With offices globally and a team of 350+ employees, Optibus fosters a collaborative culture centered on innovation, determination, and impact. As the first unicorn in public transportation technology, Optibus is driving the modernization of mass transit to make it the preferred choice for cities and passengers alike.

Why Join Optibus?

• Be part of a company revolutionizing public transportation with cutting-edge technology.
• Collaborate with global teams passionate about sustainability and innovation.
• Enjoy a dynamic and inclusive workplace culture that values growth and creativity.
• We offer a hybrid work environment, with employees expected to be in the office 3 days a week. The remaining days can be worked remotely to support work-life balance and flexibility.

Optibus is proud to be an equal opportunity employer. We hire talented individuals, regardless of gender, race, ethnicity, ancestry, age, disability, sexual orientation, gender identity or expression, cultural background, religious beliefs, or any other characteristic protected by federal, state, or local laws. It is our responsibility at Optibus to provide an inclusive and accessible interview experience for all. We will provide reasonable accommodations for all candidates in need of individualised support during the hiring process.