Lei Zheng

R

Senior Software Engineer

Relay.app

Jan 2024 - Current (2 years 5 months)

Owned core components of the agentic workflow execution engine using Python, FastAPI, and LangGraph, implementing a state-machine runtime supporting branching paths, waits, loops, retries, batching, and long-running AI agent executions with PostgreSQL and SQLAlchemy for persistent state management. Built and scaled the integration platform connecting 100+ popular SaaS apps using REST APIs, GraphQL, OAuth 2.0, and webhooks, enabling AI agents to securely read/write data across external systems via tool-calling and custom HTTP actions. Designed execution guarantees for AI agent integrations, including JWT/OAuth auth management, Redis-based rate limiting, retries with exponential backoff, idempotency keys, and graceful error recovery patterns.

R

AI Software Engineer

Relay.app

Aug 2022 - Dec 2023 (1 year 5 months)

Built AI-powered agentic workflow steps using Python, LangChain, LangGraph, OpenAI GPT-4, Claude, and Gemini, executing LLM agents as deterministic units producing schema-validated structured outputs (Pydantic, JSON Schema) consumable by downstream automation logic. Designed prompt compilation and RAG (Retrieval-Augmented Generation) pipelines using Pinecone vector database and LangChain, assembling workflow context, prior step outputs, and semantic retrieval while enforcing token budgets and output constraints. Implemented chat-based workflow authoring using LangChain agents, streaming APIs, and Server-Sent Events (SSE), where users describe automation goals in natural language and AI translates them into executable workflow graphs. Integr

B

Principal Software Engineer

Bookvid

Jul 2021 - Aug 2022 (1 year 2 months)

Led end-to-end re-architecture from a legacy PHP/DailyJS platform to a modern, AI-ready stack (Next.js, Flask, LiveKit), enabling 3x revenue growth and significantly improving scalability and reliability. Architected real-time audio/video infrastructure using LiveKit, including AI-agent-ready pipelines supporting streaming audio, data channels, and extensible hooks for STT, LLM, and TTS integrations. Designed and owned backend architecture and Postgres data models for microservices, applying advanced indexing, caching, and query optimization to support high-concurrency real-time workloads. Built core meeting lifecycle systems (hosting, booking, analytics, logging) with support for real-time transcription, automated insights, and AI-driven w

Senior Software Engineer

Velocity Global

May 2020 - Jul 2021 (1 year 3 months)

Served as a lead engineer on the Customer Experience Platform (CXP), a multi-tenant SaaS product supporting internal and external users, built with React, Python, GraphQL (Strawberry), PostgreSQL, Docker, and AWS. Designed and implemented scalable backend microservices in Python using Django and Pydantic, processing high-volume transactional and analytical data with strong reliability and performance guarantees. Architected core GraphQL layers using Strawberry GraphQL to support route optimization, billing automation, and efficient data access across complex domain models. Led integration of enterprise AI search and knowledge retrieval using Glean, applying prompt engineering and API orchestration to deliver accurate, context-aware response

Software Engineer

Bright Health

Mar 2019 - May 2020 (1 year 3 months)

Built and maintained full-stack components of NeueHealth's value-based care platform, using React, GraphQL, Golang, PostgreSQL/Oracle, Docker, and AWS, supporting 500K+ consumers across ACA, Medicare, and Medicaid. Designed and implemented scalable backend microservices in Golang, processing high-volume clinical and claims data with strong reliability and performance guarantees. Developed frontend features in React for care coordination, internal operations, and clinical workflows, collaborating closely with product and design teams. Architected GraphQL APIs to unify data access across payer, provider, and billing systems, reducing frontend complexity and improving system efficiency. Delivered HIPAA-compliant systems, ensuring secure PHI ha

Software Engineer

Tenna

Jan 2018 - Mar 2019 (1 year 3 months)

Delivered the MVP for an advanced asset tracking solution within 6 months using React, Python (Flask), and AWS, driving adoption among construction and equipment management companies. Led migration of legacy Angular front-end to React with TypeScript, Redux, and SCSS, improving platform maintainability and enabling faster feature development. Designed and implemented microservice architecture using Python, FastAPI, Docker, and Kubernetes, significantly improving scalability and performance of Tenna's fleet management platform. Built service discovery and load balancing infrastructure with Consul and Envoy Proxy, enhancing system resiliency and enabling seamless horizontal scaling. Developed real-time asset tracking integrations using REST A

Software Engineer

Uber

Aug 2016 - Jan 2018 (1 year 6 months)

Built and scaled core backend services for Uber Eats, supporting real-time order lifecycle, restaurant availability, and delivery coordination in high-demand markets. Developed high-throughput microservices using Python and Java, integrating with distributed systems handling millions of events per day. Worked on data pipelines and service logic powering order matching, pricing, and ETA calculations, balancing performance, accuracy, and reliability. Implemented APIs and internal tools to improve merchant onboarding, menu management, and operational visibility for restaurants. Collaborated closely with product, data, and infrastructure teams to ship features incrementally in a fast-moving, production-heavy environment. Contributed to system r

Software Engineer Intern

Yahoo!

Sep 2015 - Aug 2016 (1 year)

Contributed to backend services supporting Yahoo Mail and Yahoo News, working on features used by millions of daily active users. Built and optimized APIs and data-processing components using Python, Java, and SQL, improving content delivery and system reliability. Worked on large-scale data pipelines related to content indexing, personalization, and user engagement analytics. Assisted with performance tuning and bug fixes in high-traffic services powering search, media, and content platforms. Collaborated with senior engineers in a production environment, gaining hands-on experience with distributed systems, A/B testing, and data-driven product iteration.

About

Detail

Timeline

Résumé