# Kui Cheung > Staff Software Engineer at Mainstay Location: Peoria, Arizona, United States Profile: https://flows.cv/kui Staff Software Engineer with 10+ years building scalable cloud infrastructure, distributed systems, and AI-powered platforms. Currently architecting enterprise AI agent workflows at Mainstay, where I lead full-stack development from FastAPI backends to React dashboards. What I do: I specialize in taking complex technical challenges and turning them into production systems that scale. Whether it's migrating entire cloud infrastructures with zero downtime, building AI agent orchestration platforms, or designing authentication systems for thousands of users—I focus on architecture that's both elegant and pragmatic. Recent work: Built an enterprise AI agent workflow platform with hierarchical session management and real-time streaming for automated property valuation Led AWS infrastructure migration from Kubernetes to ECS, modernizing CI/CD pipelines and improving deployment velocity Designed SSO authentication systems with Keycloak, unifying identity management across multiple applications Architected high-performance listings management platforms supporting institutional clients at scale Technical toolkit: Languages: Java, TypeScript, Golang, Python | Cloud: AWS (ECS, Lambda, S3, DynamoDB) | AI/ML: Strands Agents, LangChain, GPT-5 | Infrastructure: Terraform, Kubernetes, Docker | Databases: PostgreSQL, MySQL, Snowflake Previously built real-time systems at Zillow, enterprise platforms at Opendoor, and scaled job infrastructure at Glassdoor. Always interested in connecting with engineers working on interesting problems in cloud architecture, AI/ML systems, and developer platforms. ## Work Experience ### Staff Software Engineer @ Mainstay Jan 2023 – Present Leading full-stack development and cloud infrastructure for a proptech platform serving institutional real estate clients. AI Agent Workflow Platform • Architected enterprise AI agent system with hierarchical session management and real-time streaming for automated property valuation. Built full-stack platform using FastAPI, React/TypeScript, and hybrid PostgreSQL + S3 storage. Integrated multi-agent workflows into production job orchestration system generating automated Listing Price Reports at scale. Infrastructure & Platform Engineering • Led AWS infrastructure migration from Opendoor environment to Mainstay with zero downtime. Migrated applications from Kubernetes to ECS using Terraform and modernized CI/CD from Concourse to GitHub Actions. Designed enterprise SSO solution with Keycloak and custom authentication extensions. Built high-performance listings management platform for bulk property listings with workflow automation and MLS integrations. Key technologies: Python, TypeScript, FastAPI, React, Strands Agents, LangChain, AWS (ECS, S3, Lambda), PostgreSQL, Terraform, GitHub Actions, Keycloak ### Senior Software Engineer @ Opendoor Jan 2022 – Jan 2023 | Remote Enterprise Team • Designed and built a user management platform, integrating authentication, organization structuring, and role-based access control. • Led backend development for offers management, optimizing high-volume transaction processing and integrating third-party tools like SalesScreen. • Developed a transaction history service with a UI for real-time tracking of offers and deal history. ### Senior Software Engineer @ Zillow Jan 2018 – Jan 2022 Agent Platform • Led the design and development of Zillow’s touring infrastructure, integrating with ShowingTime. • Designed an event streaming pipeline to enhance real-time data processing. • Overhauled Zillow’s notification system, reducing implementation time from one week to one hour. • Developed core email/SMS messaging services for real estate agents. ### Senior Software Engineer @ YapStone Jan 2017 – Jan 2018 | Walnut Creek, CA Trust and safety team - Built an automated document verification system for onboarding compliance. - Migrated risk services to a new platform using Provenir as the decision engine. ### Senior Software Engineer @ Glassdoor Jan 2015 – Jan 2017 | Mill Valley, CA Salaries - Develop persistent layer for salary estimates of individual job listing - Develop various backend components of Know Your Worth platform Mobile Easy Apply Platform - Develop backend components of mobile easy apply platform - Improves mobile easy apply system to enable over 1 million job listings - Design and develop automation components to simplify job application process for users(etc. registration, resume upload, pdf compression) Jobs Platform - implements various features to improve jobs aggregation system performance and efficiency - Develop admin tools for configuring and monitoring jobs aggregration system ### Software Engineer @ Glassdoor Jan 2014 – Jan 2015 | San Francisco Bay Area Jobs Platform ## Education ### Bachelor's degree in Computer Science San José State University Jan 2011 – Jan 2013 ## Contact & Social - LinkedIn: https://linkedin.com/in/kui-cheung-ba366957 --- Source: https://flows.cv/kui JSON Resume: https://flows.cv/kui/resume.json Last updated: 2026-03-22