Senior Full-Stack Software Engineer

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.

Ready to shape the future of real estate with AI? Join Mainstay and help us redefine what’s possible in the single family rental space. If you thrive on solving complex problems and want to make a tangible impact in a fast-growing industry, we’d love to hear from you - apply now and let’s move the industry forward, together!

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! You’ll 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.

We’re looking for someone who can use AI to efficiently ship features across the stack 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.

In this role you will

• Contribute to all phases of product development, from ideation and prototyping to implementation and iteration

• Design reliable, scalable backend services to support AI-powered features in production

• Build and evolve scalable backend services and APIs that aggregate, enrich, and serve large, complex real estate datasets

• Develop and refine frontend and backend product experiences that make sophisticated data intuitive, trustworthy, and actionable

• Evaluate and benchmark LLM performance across latency, cost, accuracy, and hallucination rates

• Own technical decisions for systems that sit at the center of Mainstay’s SaaS platform and directly influence investor decision-making

• Partner closely with product managers, designers, data science, and data engineering to translate business needs into durable technical solutions

• Improve system reliability, performance, and maintainability as the platform scales

• Modernize and automate legacy real estate workflows by replacing manual analysis with software-driven insights

• Mentor other engineers through code reviews, technical guidance, and shared ownership of team standards

What we’re looking for

• 5+ years of experience building and shipping production-grade software in fast-paced and early-stage start up

• Proven, hands-on experience developing and deploying production-ready AI features

• Highly proficient with AI-first thinking and software development best practices

• Strong full-stack engineering skills with a backend-first orientation

• Deep experience designing, building, and operating scalable backend systems, ideally in Python

• Solid frontend experience with React or similar modern frameworks

• Experience working with data-heavy, analytics-driven, or workflow-oriented systems

• Strong technical judgment and the ability to balance speed, correctness, and long-term maintainability

• Clear, thoughtful communication skills for a remote, highly collaborative team

• A proactive, ownership-driven approach to ambiguous problems

This role is a great fit if

• You want to work on high-leverage systems that directly shape how institutional investors deploy capital

• You enjoy owning complex technical problems from problem definition through production impact

• You like working at the intersection of data, product, and business decision-making

• You’re comfortable influencing technical direction and raising the bar for engineering quality

• You thrive in environments with autonomy, responsibility, and evolving priorities with strong ownership

Not a great fit if

• You lack strong backend experience or are uncomfortable owning production systems in Python

• You prefer narrowly scoped tasks over end-to-end ownership

• You avoid frontend or product-facing work You struggle with ambiguity, changing requirements, or close cross-functional collaboration

• You prefer highly rigid processes and minimal iteration

Tools we use

• Languages: Python, TypeScript

• Backend: FastAPI, Django

• Frontend: React, Next.js

• Data: Airflow, dbt, Snowflake, PostgreSQL

• Infra: AWS, Terraform

• Tooling: GitHub

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 mainstay-recruiting@opendoor.com