Senior Software Engineer, Applied AI

San Jose, CA - USA

Yearly Salary: USD 158080 - 232500

Posted on: 30+ days ago

Vacancies: 1 Vacancy

The job posting is outdated and position may be filled

Department:

Engineering

Job Summary

About Mainstay

Mainstay is the leading market intelligence platform purpose built for buying managing and selling homes in the single family rental industry. As an AI native company we turn complex data into clarity that helps the industry move forward with confidence. Founded within Opendoor Mainstay launched as an independent company in 2024 and recently raised a Series A round led by Khosla Ventures.

About the role

What you should expect as a full-stack senior software engineer - maximum agency tight feedback loops with customers and no shortage of product challenges that directly translate to business value! Youll have the opportunity to design build and ship complex AI-powered workflow management systems and tools that enable our operations team to execute at scale.

Were looking for someone who can both fine-tune and optimize models and ship reliable production ready AI features end to end - from retrieval pipelines and guardrails to backend systems and user facing product experiences.

Our products are built with Python Typescript and React on AWS.

What youll do

In this role youll be responsible for both shaping new AI-powered product experiences and ensuring theyre reliable at scale. That means fine-tuning and optimizing models for our domain designing retrieval pipelines and guardrails and building the backend systems that make these features production-ready. Youll work closely with product managers designers and operators to bring AI features from idea to launch balancing innovation with stability.

In this role you will:

Contribute to all phases of product development from ideation and prototyping to implementation and iteration
Build and evolve both frontend product experiences and backend services that power them
Fine-tuning existing models and optimize their performance for Mainstay use cases
Design reliable scalable backend services to support AI-powered features in production
Leverage AI to modernize and automate legacy workflows in the real estate industry
Evaluate and benchmark LLM performance across latency cost accuracy and hallucination rates
Tune prompts chain-of-thought logic and implement retrieval strategies such as RAG and vector stores
Monitor performance safety and cost of LLM-driven features in production environments
Define and build useful LLM-powered experiences in partnership with cross-functional teams
Mentor and support the growth of other engineers on the team
Collaborate closely with product managers designers and operators to identify and solve customer pain points

What were looking for

5 years of experience building and delivering production-grade software ideally in fast-paced high-growth startup environment
At least 3 years of hands-on experience developing and deploying production-ready AI features (LLM applications fine-tuning RAG systems guardrails evals etc.)
Strong full-stack engineering skills with a focus on backend scalability and system reliability
Experience fine-tuning and deploying LLMs
Deep understanding of LLM evaluation methods including prompt testing retrieval precision hallucination detection and cost/performance tradeoffs
Experience building custom eval pipelines using techniques like model-as-a-judge or embedding similarity
Hands-on work with agentic frameworks (e.g. LangGraph AutoGen CrewAI) or custom agent systems
Strong full-stack engineering skills with a focus on scalable systems and adaptability
Clear concise communicator - essential for our remote highly collaborative team
Proactive and ownership-driven - comfortable navigating ambiguity and shifting priorities
Customer-focused mindset with a drive to build solutions that solve real problems
Experience with AI/ML tools or APIs; bonus if youve worked with Python-based RAG voice agents or AI task automation

Bonus points if

Experience working with retrieval-augmented generation (RAG) pipelines
Exposure to building or integrating voice agents
Familiarity with task automation powered by AI
Strong Python background with applied AI or ML workflows

#LI-AW

Mainstay Built on Trust

At Mainstay trust is at the core of everything we do. We build trust with everyone -- from candidates to employees to partners. We believe in fairness and openness throughout our hiring process evaluating candidates based on qualifications without regard to race color religion national origin age gender marital status disability veteran status sexual orientation gender identity or any other protected status. Our privacy practices describe how we handle applicant information you can find the policy details for California residents here.

We are committed to providing reasonable accommodations throughout our recruitment processes for candidates with disabilities pregnancy religious beliefs or other reasons protected by applicable laws. If you require assistance or a reasonable accommodation please contact us at

Required Experience:

Senior IC

About MainstayMainstay is the leading market intelligence platform purpose built for buying managing and selling homes in the single family rental industry. As an AI native company we turn complex data into clarity that helps the industry move forward with confidence. Founded within Opendoor Mainsta...