Founding Engineer – Backend & AI Systems

Join to apply for the Founding Engineer – Backend & AI Systems role at Relixir (YC X25)

Join to apply for the Founding Engineer – Backend & AI Systems role at Relixir (YC X25)

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This range is provided by Relixir (YC X25). Your actual pay will be based on your skills and experience — talk with your recruiter to learn more.

Base pay range

$150,000.00/yr - $250,000.00/yr

Location: In-person, SF\ \ Requirement: BS in Computer Science from Top US Unverisity (Stanford, Berkeley, MIT, GeorgiaTech, etc.)
Stack: Python, FastAPI, PostgreSQL, AWS (ECS, Fargate), Qdrant, TypeScript
Backend Infrastructure
What You’ll Work On

• Building and scaling services in Python (FastAPI) with PostgreSQL as our primary database.
• Managing AWS infrastructure — primarily ECS/Fargate, Lambda, S3, and related services.
• Designing APIs for our frontend (TypeScript) and partner integrations.
  

AI/ML Engineering

• Building agentic workflows and pipelines for large-scale LLM calls (OpenAI, Gemini, Perplexity).
• Designing and maintaining RAG (Retrieval-Augmented Generation) systems using Qdrant for vector search.
• Optimizing prompt engineering, retrieval strategies, and evaluation systems.
  

The ROLE
You are not just an employee – you are a builder of the company.
You’ll be at the core of shaping Relixir’s product, technology, and trajectory – from hands-on backend and AI engineering, to collaborating on the big decisions that define our future.

• Strategic Impact – Work directly with the founders to influence technical and product direction, deciding how we scale our platform and what bets we make in AI search automation.
• End-to-End Ownership – Take ideas from rough concept to production-ready systems – APIs, infrastructure, AI agents, and everything in between. You’ll own critical backend modules and ensure they’re fast, reliable, and a joy to use.
• AI Systems Engineering – Design and deploy large-scale AI workflows – multi-agent pipelines, RAG architectures with Qdrant, and high-volume LLM call orchestration.
• Customer-Driven Development – Talk to customers, dig into their needs, and turn feedback into technical solutions that directly impact their growth.
  

About You

• 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. You move quickly, test bold ideas, and turn uncertainty into working solutions.
• True Owner — You don’t just “complete tickets.” You take full responsibility for delivering outcomes — finding a path forward even with incomplete information.
• Collaborative & Humble — You share ideas openly, listen actively, and care more about the best solution than being right. You’re confident in your skills but always learning.
  

Must-Haves

• In-person SF
• High-agency
• 3+ years of experience building backend & AI software for VC-backed startups
• Strong proficiency in Python and TypeScript
• Experience with Docker, FastAPI, PostgreSQL, and AWS
• Built and deployed a complex agentic/LLM-backed (context engineering, RAG with vector db) into production to customers
• Have completed at least one 0 -> 1 journey of a functional product
  

Nice-to-haves

• Experience working with any of AWS ECS + SQS + Fargate, QDrant, LangChain
• Entrepreneurial Mindset: Ex-founder or future founder
  

Why This Role is Special
We're Growing 166% MoM, Onboarding Monster Logos (Rippling, Airwallex, Hackerrank, Etc.), Supporting Global Marketing Teams, And On Our Way To Series A By EOY.\ \ This August, I'm Looking For The Most Cracked Top 1% Founding Engineers And Founding Customer Success/ops To Join Our Rocketship \ \ \ Here's My Pitch To You

Our product is far ahead of the competition. Companies are switching to us every week because they see the differentiation & immediate value.

Revenue pipeline is already at $X,000,000 <2 months since launch and rapidly growing. There's simply more customers than we can handle.

Customers now see Relixir as the unified solution to automate their entire SEO/GEO Growth Marketing function: a $400B market opportunity.

We're backed by Y Combinator and legendary operating investors like z21 Ventures who have built unicorns from scratch.\ \ \ Lastly, our team is a group of nonchalant, hardworking, super chill college dropouts from Berkeley who have scaled and even exited previous companies for 7-figures.

Seniority level

• Seniority level

  Mid-Senior level

Employment type

• Employment type

  Full-time

Job function

• Job function

  Engineering and Information Technology

• Industries

  Software Development

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