Founding Engineer

Job Description

About Company

Relixir is a rapidly growing company on a trajectory to Series A by the end of the year. They are experiencing 166% Month-over-Month growth and are successfully onboarding significant clients such as Rippling, Airwallex, and Hackerrank, supporting global marketing teams.

Their product is positioned as a unified solution to automate the entire SEO/GEO Growth Marketing function, addressing a $400B market opportunity. Relixir prides itself on having a product that is “far ahead of the competition,” offering clear differentiation and immediate value to customers, leading to rapid adoption. In less than two months since launch, their revenue pipeline has already reached $X,000,000 and continues to grow rapidly, indicating more customer demand than they can currently handle.

Relixir is backed by Y Combinator and distinguished operating investors like z21 Ventures, known for building unicorn companies from scratch. The core team is described as a group of “nonchalant, hardworking, super chill college dropouts from Berkeley” who possess a strong track record, having scaled and successfully exited previous companies for 7-figures.

Job Description: Founding Engineer (Backend & AI)

Location: San Francisco (Mandatory)

Requirement:
• Currently pursuing a Bachelors in Computer Science from a Top US University (e.g., Stanford, Berkeley, MIT, GeorgiaTech).

Stack:
• Languages: Python, TypeScript
• Web Framework: FastAPI
• Database: PostgreSQL
• Cloud Platform: AWS (ECS, Fargate, Lambda, S3, SQS)
• Vector Database: Qdrant

Key Responsibilities:

This role is for a Founding Engineer who will be integral to shaping Relixir’s product, technology, and overall trajectory. You will engage in both hands-on backend and AI engineering, while also contributing to strategic decisions.

1. Backend Infrastructure & Scalability:
• Building and scaling services using Python (FastAPI) with PostgreSQL as the primary database.
• Managing AWS infrastructure, primarily ECS/Fargate, Lambda, S3, and related services.
• Designing robust APIs for both the frontend (TypeScript) and various partner integrations.
• Taking end-to-end ownership of critical backend modules, ensuring they are fast, reliable, and user-friendly.

2. AI/ML Engineering & Systems Design:
• Building agentic workflows and pipelines for large-scale LLM calls using providers like OpenAI, Gemini, and Perplexity.
• Designing and maintaining RAG (Retrieval-Augmented Generation) systems leveraging Qdrant for efficient vector search.
• Optimizing prompt engineering, retrieval strategies, and developing effective evaluation systems.
• Designing and deploying large-scale AI workflows, including multi-agent pipelines and high-volume LLM call orchestration.

3. Strategic & Product Impact:
• Working directly with the founders to influence technical and product direction, including platform scaling and strategic bets in AI search automation.
• Engaging in customer-driven development by actively talking to customers, understanding their needs, and translating feedback directly into technical solutions that impact their growth.
• Taking ideas from rough concepts to fully production-ready systems, encompassing APIs, infrastructure, and AI agents.

About You (Candidate Profile):

• Deeply Curious: You actively seek to understand complex systems, customer problems, and the latest technical possibilities. Curiosity drives your best work.
• Relentlessly Driven: You thrive in early-stage chaos, move quickly, test bold ideas, and turn uncertainty into working solutions.
• True Owner: You take full responsibility for delivering outcomes, finding a path forward even with incomplete information, rather than just completing tickets.
• Collaborative & Humble: You share ideas openly, listen actively, and prioritize the best solution over being right, always learning.

Must-Haves:

• In-person SF
• High-agency
• Proven experience building backend & AI software, preferably for VC-backed startups.
• Strong proficiency in Python and TypeScript.
• Hands-on experience with Docker, FastAPI, PostgreSQL, and AWS.
• Demonstrated ability to have built and deployed a complex agentic/LLM-backed system (including context engineering, RAG with vector db) into production for customers.
• Have completed at least one 0 -> 1 journey of a functional product (taking an idea from inception to a fully functional, shipped product).

Nice-to-Haves:

• Experience working with any of AWS ECS + SQS + Fargate, Qdrant, LangChain.
• Entrepreneurial Mindset: Previous experience as a founder or aspiring to be a founder.