Senior Software Engineer – Applied AI

Job Description: Contribute to all phases of product development, from ideation and prototyping to implementation and iterationBuild and evolve both frontend product experiences and backend services that power themFine-tuning existing models and optimize their performance for Mainstay use casesDesign reliable, scalable backend services to support AI-powered features in productionLeverage AI to modernize and automate legacy workflows in the real estate industryEvaluate and benchmark LLM performance across latency, cost, accuracy, and hallucination ratesTune prompts, chain-of-thought logic, and implement retrieval strategies such as RAG and vector storesMonitor performance, safety, and cost of LLM-driven features in production environmentsDefine and build useful LLM-powered experiences in partnership with cross-functional teamsMentor and support the growth of other engineers on the teamCollaborate closely with product managers, designers, and operators to identify and solve customer pain pointsRequirements: 5+ years of experience building and delivering production-grade software, ideally in fast-paced, high-growth startup environmentAt 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 reliabilityExperience fine-tuning and deploying LLMsDeep understanding of LLM evaluation methods, including prompt testing, retrieval precision, hallucination detection, and cost/performance tradeoffsExperience building custom eval pipelines using techniques like model-as-a-judge or embedding similarityHands-on work with agentic frameworks (e.g. LangGraph, AutoGen, CrewAI) or custom agent systemsClear, concise communicator - essential for our remote, highly collaborative teamProactive and ownership-driven - comfortable navigating ambiguity and shifting prioritiesCustomer-focused mindset with a drive to build solutions that solve real problemsExperience with AI/ML tools or APIs; bonus if you've worked with Python-based RAG, voice agents, or AI task automation.Benefits: Trust is at the core of everything we do.We build trust with everyone -- from candidates to employees to partners.Providing reasonable accommodations throughout the recruitment process for candidates with disabilities, pregnancy, religious beliefs, or other reasons protected by applicable laws.