Hao Xu
Verified Expert in Engineering
Full-stack Developer
Palo Alto, CA, United States
Toptal member since September 5, 2023
Hao is a back-end engineer and full-stack veteran with a proven track record of developing services and software solutions for various companies, ranging from small startups to big top-notch corporations. His expertise spans eCommerce, social applications, games, software infrastructures, DevOps, SaaS, and algorithms. Hao is also proficient in big data, AI, and large language models (LLMs) and excels in executing projects and effectively communicating his ideas.
Portfolio
Experience
Availability
Preferred Environment
Full-stack, Web3, Ruby on Rails (RoR), Python, Go, Java, C++, Cloud, JavaScript, Algorithmic Trading
The most amazing...
...thing I've accomplished is building multiple applications for startups and large systems, supporting companies from their early stages through growth and IPOs.
Work Experience
Back-end Symfony and AWS Developer
Imagemakers Inc.
- Built many new features according to business requirements and KTLO.
- Guided and built the spammer/reCAPTCHA verification to fight against spammers.
- Oversaw the Symfony framework maintenance work and deployment flow.
- Developed new emails and enhanced a new search capability.
Senior Scala Developer | Zio Framework Expert
Dealermade LP
- Diagnosed and provided guidelines for the performance and scalability issues of the ZIO/Scala framework.
- Developed a Scala async framework solution to scale up/out the current system.
- Provided a new architecture, roadmap, and operation process/documents for the company to use in future development.
Tech Lead
Instacart
- Built the full-stack customer platform and front end for web, mobile web, iOS, and Android.
- Architected the chat and recommendation based on ML, OpenAI GPT API, private LLMA, Finetune, RAG, and LangChain.
- Contributed to the infrastructure and DevOps to ensure the Instacart platform ran smoothly.
- Served as a tech leader in building the Instcart eCommerce platform with Ruby on Rails and GraphQL, the world's biggest Ruby on Rail deployment.
- Architected and built a user authentication platform in Go, serving hundreds of millions of users.
Tech Lead
Roblox
- Built the microservice infrastructure and DevOps for the Roblox platform.
- Architected the user spammer, user suspicion detection, and prevention system.
- Improved the platform's performance and scalability to support 10x growth.
- Built next-generation mesh services in Go, handling millions of queries per second and serving hundreds of millions of users.
Tech Lead
Uber
- Spearheaded the development of the company's global real-time logistic platform for both back-end and client side.
- Built a global intelligence platform tailored for conducting competitive analyses.
- Created the next-generation driver system in Go to achieve a tenfold performance boost compared to the Node.js one.
Senior Engineer
Airbnb
- Built the async process framework based on Kafka and operated it.
- Acted as a full-stack engineer building the dev portal and pipeline.
- Created the infrastructure and DevOps for an Airbnb back end.
- Built the world's biggest travel eCommerce marketplace with Ruby on Rails and Java/Go.
CTO
Citrus Lane
- Built the Citrus Lane website to support 200,000+ users on all platforms—web, iOS, and Android.
- Developed systems to operate 100,000+ monthly subscriptions.
- Created systems for the recurring bills of 100,000+ customers.
Software Engineer
- Built the coupon ads and served billions of audience.
- Architected a pipeline to analyze the performance and results of coupon ads.
- Improved the foundation of the ad display and analytics platform.
Engineer
Yahoo!
- Led a team to build Yahoo email. I built YOS, search, and ads platforms.
- Acted as a full-stack engineer lead and built Yahoo Answers, Flickr, and many other social products.
- Built many Yahoo infrastructure data pipelines and Hadoop stacks.
Principal Engineer
Oracle
- Built and supported the global platform of the Siebel system.
- Architected the infrastructure and comm layer for the Siebel system.
- Developed the analytics platform with a team for the Siebel system.
Experience
Uber | Global Service Platforms
I worked for them as a tech lead, spearheading the development of their global real-time logistic platform, their global intelligence platform for competitive analyses, and the next-generation driver system.
Airbnb | Product and Service Infrastructure and Data Flow
http://www.airbnb.comI integrated the team as a senior engineer and tech lead, contributing to the product and service infrastructure and the communication and data flow within the company's systems.
Google | Ads Project
http://www.google.comI joined the project to combine the power of search and ads with AI technology, working on the ads UI and developing coupon ads.
Roblox | Platform Architecture
I worked at Roblox as a tech lead, handling their next-generation platform's architecture, development, and maintenance, moving from a monolithic to a microservice architecture.
Citrus Lane | Back-end Infrastructure, Website, and Apps
I joined them as a tech leader, leading the team to build the back-end infrastructure, website, and apps.
Siebel | Cross-platform Functionality
I played a crucial role in developing the cross-platform functionality for Siebel, enabling seamless operation on Linux, IBM AIX, and Microsoft Windows, with support for multiple databases, including IBM Db2, Oracle, and Microsoft SQL Server.
Subsequently, Siebel was acquired by Oracle, marking a significant milestone in its history.
Yahoo | Platform, Infrastructure, and Data Storage Systems
http://www.yahoo.comI worked at Yahoo as a principal engineer and tech lead, contributing to multiple tasks regarding the platform, infrastructure, and cloud data storage systems.
Algorithm Trading System
Student Class Selection System
Finance, Legal, and Web Scrap Project
Trading Bots
They could plug in the specific algorithms.
DMX Cat
Video Conference
Ice Diamond
Electronic Accessory
DeFi Solana Smart Contract Web3
One of the Largest Lawyer Sites
Education
Master's Degree in Computer Science
The University of New Mexico - Albuquerque, New Mexico, USA
Bachelor's Degree in Computer Science
Tsinghua University - Beijing, China
Skills
Libraries/APIs
Node.js, Stripe Development, Stripe Development, NumPy, React.js, Python API, Interactive Brokers API, TWS API, API, Ruby on Rails, Beautiful Soup, OpenAI Assistants API, Gmail API, Authorize.Net, Office 365 API, REST API, Pandas, Google Sheets API, ZIO, Django, PyQt, PySide, JSII, Crawlee, Puppeteer, OpenAI API, Google API, Solana.py, CheerioJS, Goutte, Python, Asyncio, Google Maps Development, Google Maps Development, Mapbox API, RxJava, jQuery, Vue.js
Tools
Logging, Amazon Elastic Container Service (ECS), AWS Key Management Service (KMS), Terraform, HashiCorp, Cloud Dataflow, Git, GNU Debugger (GDB), CMake, GitHub, RabbitMQ, ChatGPT, Google Analytics, Docker Hub, BigQuery, Cron, Android, Expo, Azure Active Directory B2C (ADB2C), Hashistack, Azure OpenAI Service, Amazon Simple Queue Service (SQS), Apache, Microsoft Power Apps, Zapier Development, RSpec, Java Development Kit (JDK), Amazon SageMaker, Observability Tools, FileZilla, PuTTY, Apache Tomcat, Apache Ant, IntelliJ IDEA, Google Sheets Development, Nginx, Azure Kubernetes Service (AKS), Azure, GTK, Figma, MongoDB, Elastic, Apache, Visual Studio Development, Babel, Webpack, WildFly, Microsoft Power Pages, Business Intelligence Development, Keycloak, Apache Beam, AWS IAM, CTools, Seos
Languages
Python, Go, Java, C++, Ruby, JavaScript, HTML, PHP, Rust, GraphQL, SQL, C#, TypeScript, CSS, C, Snowflake, Scala, Embedded C, Perl, Kotlin, Swift, SAML, Dart, XML, Google Apps Script, HTML5, Visual Basic, XHTML, C++, Python, Pine Script
Frameworks
Ruby on Rails, .NET, Cascades, Django, Boost, Laravel, ASP.NET, gRPC, Spark, Apache Thrift, Qt Development, Express.js, Selenium, Scrapy, Bootstrap, .NET Core, LlamaIndex, Tailwind CSS, Flutter, React Native, OAuth, IdentityServer 4, Next.js, Blazor, Electron.js, Spring Boot, Symfony, AngularJS, Django, Big Data Architecture, GStreamer, Java, Apache Struts 2, Flask, .NET MAUI, CakePHP, Spring, Redux, Hibernate, Angular
Paradigms
DevOps, Web Development, Microservices Development, ETL, API, Continuous Integration (CI), SEO, Business Intelligence Development, Serverless Architecture, Cross-Platform, Mobile App Design, Load Testing, API Observability, HIPAA Compliance, Agile Development, Automation, Automated Testing, Testing, Object-oriented Programming (OOP), Microservices Architecture
Platforms
Linux, Apache Kafka, Docker, Kubernetes, Windows Development, WordPress Development, AWS, Cloud Engineering, Firebase, BigCommerce, DigitalOcean, Heroku, Mobile App Design, iOS, Android, Mapbox, Azure, Google Ads, SharePoint Design, Algolia, HubSpot Development, MacOS, Amazon EC2, Ruby on Rails, JavaFX, Magento, Shopify, Databricks, Amazon, NetBeans, Zendesk Development, PagerDuty, Xamarin, Unix, Oracle Development, AWS Lambda, Microsoft Power Platform, Microsoft Power Automate, JVM, Linux, Blockchain, E-commerce Development, Wand
Storage
MySQL, PostgreSQL, NoSQL, Redshift, Database, Data Lakes, Cassandra, Redis, MongoDB, Google Cloud Development, Elasticsearch, AWS, Amazon S3, JSON, Alibaba Cloud, MariaDB, Database
Industry Expertise
Virtual Coaching, Accounting, Trading Systems
Other
Software Development, Software Development, Full-stack, Cloud Engineering, Distributed Systems, Machine Learning, Competitive Intelligence, Infrastructure, SaaS, Cloudflare, Architecture, Optimization, Servers, Platform as a Service (PaaS), Web Scraping, APIs, CI/CD Pipelines, Data Structures, Algorithms, Data Engineering, Orchestration, Web Development, Linear Algebra, Data Scraping, Web Development, OpenAI, System Design, Back-end Developers, OpenAI GPT-3 API, GPT-4, Stripe Payments, Artificial Intelligence, Artificial Intelligence, Data Science, RAG, Generative Pre-trained Transformers (GPT), Web Services, Algorithms, Data Science, Deep Learning, Data Science, Blade Templates, Scraping, E-commerce marketing, Back-end Developers, LLM, MERN Stack, Interim CTOs, Bots, Cloud Infrastructure, Full-stack, Reddit, Google Drive Development, Integration, Content Management Systems (CMS), API Integration, Google Cloud Functions, Trading, TradingView Development, Cryptocurrency, Prompt Engineering, Gmail, Email, SDK Development, SDKs, Serverless, Pinecone, Poetry, Computer Networking, System Security, Software Engineering, Software Architecture, Navigation, Electric Vehicles, Fivetran, Identity & Access Management (IAM), OpenID Connect (OIDC), Duende, SAML-auth, SecOps, Mobile App Design, Advisory, Leadership, Scalability, Technical Leadership, Startup Development, Coaching, Engineering, Process Development, Web Development, Google Tag Manager, Google Analytics 4 (GA4), Office 365, PWA, Progressive Web Applications (PWAs), Gemini API, DNS, htaccess, GoDaddy, SEO Tools, Hardware, Firmware, Low-level Programming, USB, MDM, Jamf, Mobile Device Management (MDM), Fintech Development, Profiling, Embedded Rust, Embedded Systems Engineering, Artificial Intelligence, Accessibility Development, Monitoring, Machine Learning Operations (MLOps), OpenTelemetry, Data Warehouse, Prometheus, Website Data Scraping, Solana, Crypto, Containers, Stable Diffusion, Marketing Technology (MarTech), ElevenLabs Solutions, Chatbot Development, Live Chat, eBay, HL7, Trading Bots, Big Data Architecture, Big Data Architecture, Data Science, Data Handling, Concurrency, Generative Artificial Intelligence (GenAI), Containerization, Embedded Software Engineering, Decentralized Finance (DeFi), Finance, Equities, Equity Trading, Hedge Funds, Options Trading, Profit & Loss (P&L), Stock Market Consulting, Financial Software Development, Trade Finance, Fund Management, Tickers, Stock Trading, FastAPI, Performance Tuning, WebSockets, Time Series Modeling, Image Generation, SOC 2( Service Organization Control), Mapbox SDK, Middleware, Jetpack Compose, Quantitative Analysis, Data Science, MVC Frameworks, Quarkus, Large Scale Distributed Systems, SSO Engineering, Technical Architecture, Technical Writing, Mobile Apps, Large-scale Projects, Social Security, IDP, API Connectors, Cloud Architecture, Airtable, PDF, Front-end, Team Leadership, Relational Database Services (RDS), SLAM, Simultaneous Localization & Mapping (SLAM), Dynamic Load Balancing, Plugins, System Security, LangChain, DDS, PDF Scraping, Midjourney, Strapi, Web3, Analysis, Dashboard, AI Website Builders, Buffer Management, ExpressIF, Bluetooth, ESP32, ACH Payments, Google Software, PayPal Development, Payment APIs, Smart Contract Development
How to Work with Toptal
Toptal matches you directly with global industry experts from our network in hours—not weeks or months.
Share your needs
Choose your talent
Start your risk-free talent trial
Top talent is in high demand.
Start hiring