Hao Xu, Developer in Palo Alto, CA, United States
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Hao Xu

Verified Expert  in Engineering

Full-stack Developer

Location
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 e-commerce, 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

Dealermade LP
ZIO, Scala, Profiling, Java Development Kit (JDK), JavaFX
Instacart
Ruby, JavaScript, Amazon Web Services (AWS), OpenAI, Back-end, OpenAI GPT-3 API...
Roblox
AWS IAM, Neto, OpenAI, Machine Learning, Infrastructure, Cloud, System Design...

Experience

Availability

Part-time

Preferred Environment

Linux, Full-stack, Web3, Ruby on Rails (RoR), Python, Go, Java, C++, Cloud, 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

Senior Scala Developer - Zio Framework Expert

2024 - 2024
Dealermade LP
  • diagnosis and provide guideline for the performance/scalability issue of zio scala framework.
  • developed a scala async framework solution to scale up/out the current system.
  • provide a new architecture, roadmap and operation process/documents for the future development for the coming years tailed for the company.
Technologies: ZIO, Scala, Profiling, Java Development Kit (JDK), JavaFX

Tech Lead

2020 - 2022
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.
Technologies: Ruby, JavaScript, Amazon Web Services (AWS), OpenAI, Back-end, OpenAI GPT-3 API, OpenAI GPT-4 API, Linux, Stripe API, Stripe Payments, Artificial Intelligence (AI), AI Programming, Data Scientist, Retrieval-augmented Generation (RAG), Generative Pre-trained Transformers (GPT), Continuous Integration (CI), Web Services, Data Science, GitHub, Deep Learning, Data Analytics, NumPy, RabbitMQ, Laravel, Blade Templates, React, ChatGPT, Midjourney, Firebase, TypeScript, CSS, Scraping, eCommerce, Google Analytics, Search Engine Optimization (SEO), gRPC, Snowflake, Back-end Development, Redis, Spark, Large Language Models (LLMs), Express.js, MERN Stack, MongoDB, Google Cloud, Bots, Cloud Infrastructure, Selenium, Full-stack Development, Docker Hub, Reddit API, Reddit, PostgreSQL, BigQuery, Business Intelligence (BI), Rails Engines, Google Drive, Content Management Systems (CMS), API Integration, Beautiful Soup, Google Cloud Functions, Cron, Elasticsearch, OpenAI Assistants API, Prompt Engineering, Gmail API, Gmail, Email, SDK Development, SDKs, Amazon DynamoDB, Serverless Architecture, Serverless, Pinecone, LlamaIndex, Poetry, Computer Networking, Software Engineering, Tailwind CSS, Android Studio, Cross-platform, Mobile Development, Mobile, Software Architecture, iOS, Android, Kotlin, Flutter, React Native, Swift, Mapbox, Navigation, Electric Vehicles, Fivetran, Expo, Azure, Identity & Access Management (IAM), Azure Active Directory B2C (ADB2C), OpenID Connect (OIDC), SAML, OAuth 2, Duende, IdentityServer 4, SAML-auth, SecOps, Next.js, Hashistack, AI Website Builders, Mobile App Development, Leadership, Scalability, Technical Leadership, Startups, Coaching, Engineering, Process Development, Project Management, Azure OpenAI Service, Blazor, Load Testing, Web Scalability, Amazon Simple Queue Service (SQS), Kafka Streams, Google Analytics 4, Microsoft Power Apps, SharePoint, Office 365, Office 365 API, APIs, REST APIs, CTO, PWA, Progressive Web Applications (PWA), Electron, Algolia, Gemini API, DNS, SEO Tools, Django, Spring Boot, Pandas, Google Sheets API, Hardware, Low-level Programming, MacOS, MDM, Jamf, Mobile Device Management (MDM), Zapier, Scala, ZIO, Profiling, Amazon EC2, Amazon S3 (AWS S3), AngularJS, RSpec, Solidus, Java Development Kit (JDK), JavaFX

Tech Leader

2019 - 2020
Roblox
  • Built the microservice infrastructure and DevOps for the Roblox platform.
  • Architected the user spammer, user suspicion detection, and prevention system.
  • Improved the performance and scalability of the platform to support 10x growth.
Technologies: AWS IAM, Neto, OpenAI, Machine Learning, Infrastructure, Cloud, System Design, Linux, GNU Debugger (GDB), Boost, CMake, Stripe API, Artificial Intelligence (AI), Continuous Integration (CI), Web Services, C#, GitHub, Deep Learning, Data Analytics, NumPy, RabbitMQ, ASP.NET, gRPC, Snowflake, Back-end Development, Redis, Spark, Apache Thrift, Qt, Google Cloud, Bots, Cloud Infrastructure, Docker Hub, BigQuery, Integration, Content Management Systems (CMS), Cron, Elasticsearch, Gmail API, Gmail, Email, Back-end, .NET Core, SDK Development, SDKs, Amazon DynamoDB, Serverless Architecture, Serverless, Computer Networking, Software Engineering, Android Studio, Cross-platform, Mobile Development, Mobile, Software Architecture, iOS, Android, Swift, Azure, Identity & Access Management (IAM), Azure Active Directory B2C (ADB2C), OpenID Connect (OIDC), SAML, OAuth 2, Duende, IdentityServer 4, SAML-auth, SecOps, Next.js, Hashistack, Leadership, Scalability, Technical Leadership, Startups, Coaching, Engineering, Process Development, Project Management, Azure OpenAI Service, Blazor, Load Testing, Web Scalability, Amazon Simple Queue Service (SQS), Kafka Streams, Google Tag Manager, Google Analytics 4, Microsoft Power Apps, SharePoint, Office 365, Office 365 API, APIs, REST APIs, CTO, PWA, Progressive Web Applications (PWA), DNS, SEO Tools, HubSpot, Pandas, Google Sheets API, Windows, Low-level Programming, MacOS, MDM, Mobile Device Management (MDM), Profiling, Amazon EC2, Amazon S3 (AWS S3), Java Development Kit (JDK)

Tech Leader

2016 - 2019
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.
Technologies: C++, Java, Go, Node.js, Cloudflare, Architecture, Logging, WordPress, Optimization, Servers, Hosting, Dynamic Load Balancing, Microservices, Platform as a Service (PaaS), Plugins, Rust, Blockchain, Web Scraping, APIs, ETL, Django, Redshift, Amazon Web Services (AWS), Amazon Elastic Container Service (Amazon ECS), ClickHouse, PKI, CI/CD Pipelines, AWS Key Management Service (KMS), Terraform, HashiCorp, Keycloak, GraphQL, Data Structures, SQL, Algorithms, Data Pipelines, Data Engineering, Data Lakes, Cloud Dataflow, Google Cloud Platform (GCP), Orchestration, LangChain, Apache Beam, Webhooks, API Architecture, Linear Algebra, Data Scraping, Web Development, Machine Learning, Git, Linux, GNU Debugger (GDB), Boost, DDS, CMake, Stripe API, Stripe Payments, Artificial Intelligence (AI), AI Programming, Data Scientist, Continuous Integration (CI), Web Services, Data Science, GitHub, Data Analytics, NumPy, RabbitMQ, PDF Scraping, Laravel, Blade Templates, React, Firebase, TypeScript, CSS, Scraping, eCommerce, BigCommerce, Google Analytics, Search Engine Optimization (SEO), gRPC, C, Snowflake, Back-end Development, Cassandra, Redis, Spark, Apache Thrift, Embedded C, Express.js, MERN Stack, MongoDB, Google Cloud, Bots, Cloud Infrastructure, Selenium, Full-stack Development, Docker Hub, Reddit, PostgreSQL, BigQuery, Business Intelligence (BI), Google Drive, Bootstrap, Content Management Systems (CMS), Strapi, API Integration, Beautiful Soup, Google Cloud Functions, Cron, Elasticsearch, Gmail API, Gmail, Email, Back-end, SDK Development, SDKs, Amazon DynamoDB, Serverless Architecture, Serverless, Computer Networking, Datagram Transport Layer Security (DTLS), Software Engineering, Android Studio, Cross-platform, Mobile Development, Mobile, Software Architecture, iOS, Android, Flutter, React Native, Swift, Mapbox, Navigation, Electric Vehicles, Expo, Identity & Access Management (IAM), OpenID Connect (OIDC), SAML, OAuth 2, SAML-auth, SecOps, Hashistack, Mobile App Development, Buffer Management, Leadership, Scalability, Technical Leadership, Startups, Coaching, Engineering, Process Development, Project Management, Load Testing, Web Scalability, Amazon Simple Queue Service (SQS), Kafka Streams, Google Ads, Google Tag Manager, Google Analytics 4, REST APIs, CTO, PWA, Progressive Web Applications (PWA), DNS, htaccess, SEO Tools, HubSpot, Spring Boot, Pandas, Google Sheets API, C#, Low-level Programming, MacOS, Jamf, Mobile Device Management (MDM), Zapier, Profiling, Amazon EC2, Amazon S3 (AWS S3), AngularJS, betting software, Java Development Kit (JDK), JavaFX

Senior Engineer

2017 - 2018
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.
Technologies: Ruby, Java, Machine Learning, Amazon Web Services (AWS), Apache Kafka, Linux, Boost, CMake, Stripe API, Stripe Payments, Data Scientist, Continuous Integration (CI), Web Services, GitHub, Data Analytics, NumPy, RabbitMQ, Firebase, TypeScript, CSS, eCommerce, Google Analytics, Search Engine Optimization (SEO), Snowflake, Angular, Back-end Development, Cassandra, Scala, Redis, Spark, Apache Thrift, Google Cloud, Heroku, Bots, Cloud Infrastructure, Selenium, Full-stack Development, Docker Hub, Rails Engines, Google Drive, Scrapy, Integration, API Integration, Beautiful Soup, Google Cloud Functions, Cron, Elasticsearch, Gmail API, Email, Back-end, SDK Development, SDKs, Amazon DynamoDB, Serverless Architecture, Serverless, Computer Networking, Software Engineering, Android Studio, Cross-platform, Mobile Development, Mobile, Software Architecture, iOS, Android, Kotlin, Flutter, React Native, Swift, Mapbox, Navigation, Expo, OpenID Connect (OIDC), SAML, OAuth 2, SAML-auth, SecOps, Mobile App Development, Scalability, Startups, Coaching, Engineering, Process Development, Project Management, Load Testing, Web Scalability, Amazon Simple Queue Service (SQS), Kafka Streams, Google Tag Manager, Google Analytics 4, Office 365, APIs, REST APIs, PWA, Progressive Web Applications (PWA), GoDaddy, SEO Tools, HubSpot, Spring Boot, Pandas, MacOS, Mobile Device Management (MDM), Profiling, Amazon EC2, Amazon S3 (AWS S3), RSpec, Solidus, Java Development Kit (JDK)

CTO

2013 - 2015
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.
Technologies: PHP, Node.js, BigCommerce, Back-end Development, Redis, Express.js, MERN Stack, MongoDB, CTO, Google Cloud, Heroku, Bots, Cloud Infrastructure, Selenium, Full-stack Development, Business Intelligence (BI), Perl, Scrapy, Integration, Bootstrap, Content Management Systems (CMS), Strapi, API Integration, Beautiful Soup, Google Cloud Functions, Elasticsearch, Email, .NET Core, SDK Development, Software Engineering, Mobile, Software Architecture, iOS, Android, Authorize.net, OAuth 2, SecOps, CTools, Leadership, Technical Leadership, Startups, Coaching, Process Development, Project Management, Load Testing, Web Scalability, Google Ads, Google Tag Manager, Google Analytics 4, Office 365, Office 365 API, APIs, PWA, Progressive Web Applications (PWA), htaccess, GoDaddy, SEO Tools, HubSpot, MacOS, Symfony, Amazon EC2

Software Engineer

2012 - 2012
Google
  • 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.
Technologies: Java, C++, JavaScript, Algorithms, Linux, GNU Debugger (GDB), Boost, CMake, Artificial Intelligence (AI), Data Scientist, Web Services, Data Science, GitHub, Search Engine Optimization (SEO), gRPC, C, Back-end Development, Cloud Infrastructure, Business Intelligence (BI), Google Drive, Integration, Content Management Systems (CMS), Elasticsearch, Gmail API, Gmail, SDK Development, Software Engineering, Software Architecture, Android, OAuth 2, SecOps, Scalability, Process Development, Load Testing, Web Scalability, Google Ads, Google Tag Manager, Google Analytics 4, APIs, htaccess, SEO Tools, AngularJS

Engineer

2005 - 2011
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.
Technologies: PHP, JavaScript, C++, Java, Algorithms, Linux, GNU Debugger (GDB), Boost, CMake, Artificial Intelligence (AI), GitHub, C, Back-end Development, Qt, Bots, Cloud Infrastructure, Full-stack Development, Reddit API, Perl, Content Management Systems (CMS), Elasticsearch, SDK Development, Software Engineering, Software Architecture, iOS, Android, Load Testing, Web Scalability, htaccess, Symfony, JavaFX

Principal Engineer

2001 - 2005
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.
Technologies: C++, Java, JavaScript, Linux, GNU Debugger (GDB), Boost, GitHub, Back-end Development, Google Cloud, Integration, Load Testing, Low-level Programming, JavaFX

Uber | Global Service Platforms

Uber, the leading company in the ride-sharing and gig economy, is driven by the concept of movement. Movement fuels the organization and is an integral part of its identity. They are constantly innovating and improving how they facilitate transportation, enabling customers to reach their desired destinations, acquire the things they need, and provide earning opportunities in locations across the globe. They strive to deliver these services in real time.

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.com
Airbnb's vision is to create a world where anyone can belong anywhere they go. It is built around the idea that everyone deserves to experience the perfect trip, choosing their accommodations, activities, and connections. With this in mind, they empower millions globally to become entrepreneurs by utilizing their spaces, interests, and skills. This is the audacious and rewarding mission to which Airbnb's diverse team is dedicated.

I 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.com
Google's mission is to organize the vast amount of worldwide information and make it universally accessible and helpful. With billions of users in mind, they continuously strive to develop groundbreaking products and cutting-edge tools that shape the future.

I 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

Roblox reimagines how people come together by enabling individual connections and fostering meaningful relationships in the Meta world. Roblox employees tackle complex questions and drive incredible innovation.

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

Citrus Lane is a startup providing children subscriptions. It serviced tens of thousands of children subscriptions and experienced a remarkable tenfold growth.

I joined them as a tech leader, leading the team to build the back-end infrastructure, website, and apps.

Siebel | Cross-platform Functionality

Siebel, the leading global customer relationship management (CRM) company, specializes in building enterprise software solutions.

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.com
Yahoo's media, technology, and business platforms connect hundreds of millions of people worldwide to the things they love. With apps and sites like Yahoo Sports, Yahoo Finance, Yahoo Fantasy, and Yahoo Mail and a powerful, open platform that connects brands and publishers to passionate fans, they're all about putting an exclamation point on what users are into.

I 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

I built a trading system that generated signals based on the owner's various algorithms and did the auto trading. It was built on top of ib_insync. The system provides a framework for owners to plug in algorithms.

Student Class Selection System

An internal web system that allows students to select available classes. I built it on top of MySQL and Ruby on Rails. It comes with an admin dashboard, and it enables 500 students to choose among 20 classes based on various criteria and capacities.

Finance, Legal, and Web Scrap Project

A whole system to scrap many finance and legal systems with special requirements. This also involved a website for crud, alert, display, user management, and real-time communication to end users massively and swiftly.

Trading Bots

A Python-based trading system for trading. I utilized IB trading APIs, pine script on trading views, and other technologies. This is a system built for a private team.
They could plug in the specific algorithms.

DMX Cat

I designed, built, deployed, and maintained high-quality iOS and Android apps for Bluetooth and hardware applications. I also developed Mac, Windows, and Linux applications, as well as hardware and firmware. Additionally, I used C++ and client-side technologies in my work.
1998 - 2001

Master's Degree in Computer Science

The University of New Mexico - Albuquerque, New Mexico, USA

1993 - 1998

Bachelor's Degree in Computer Science

Tsinghua University - Beijing, China

Libraries/APIs

Node.js, Stripe, Stripe API, NumPy, React, Interactive Brokers API, TWS API, Reddit API, Rails Engines, Beautiful Soup, OpenAI Assistants API, Gmail API, Authorize.net, Office 365 API, REST APIs, Pandas, Google Sheets API, ZIO, Vue, Python API

Tools

Logging, Amazon Elastic Container Service (Amazon 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 Studio, Expo, Azure Active Directory B2C (ADB2C), Hashistack, Azure OpenAI Service, Amazon Simple Queue Service (SQS), Kafka Streams, Microsoft Power Apps, Zapier, RSpec, Java Development Kit (JDK), Keycloak, Apache Beam, AWS IAM, CTools

Frameworks

Ruby on Rails (RoR), .NET, Cascades, Django, Boost, Laravel, ASP.NET, gRPC, Spark, Apache Thrift, Qt, Express.js, Selenium, Scrapy, Bootstrap, .NET Core, LlamaIndex, Tailwind CSS, Flutter, React Native, OAuth 2, IdentityServer 4, Next.js, Blazor, Electron, Spring Boot, Symfony, AngularJS, Angular

Languages

Python, Go, Java, C++, Ruby, JavaScript, HTML, PHP, GraphQL, SQL, C#, TypeScript, CSS, C, Snowflake, Scala, Perl, Kotlin, Swift, SAML, Rust, Embedded C, Python 3, Pine Script

Paradigms

DevOps, Hosting, Microservices, ETL, API Architecture, Continuous Integration (CI), Data Science, Search Engine Optimization (SEO), Business Intelligence (BI), Serverless Architecture, Cross-platform, Mobile Development, Load Testing

Platforms

Linux, Apache Kafka, Docker, Windows, WordPress, Amazon Web Services (AWS), Google Cloud Platform (GCP), Firebase, BigCommerce, DigitalOcean, Heroku, Mobile, iOS, Android, Mapbox, Azure, SharePoint, Algolia, HubSpot, MacOS, Amazon EC2, Solidus, JavaFX, Blockchain, Kubernetes, Neto, Wand

Storage

MySQL, PostgreSQL, NoSQL, Redshift, Data Pipelines, Data Lakes, Cassandra, Redis, MongoDB, Google Cloud, Elasticsearch, Amazon DynamoDB, Amazon S3 (AWS S3), ClickHouse

Industry Expertise

Project Management

Other

Software Development, Software, Full-stack, Cloud, 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, Webhooks, Linear Algebra, Data Scraping, Web Development, OpenAI, System Design, Back-end, OpenAI GPT-3 API, OpenAI GPT-4 API, Stripe Payments, Artificial Intelligence (AI), AI Programming, Data Scientist, Retrieval-augmented Generation (RAG), Generative Pre-trained Transformers (GPT), Web Services, Deep Learning, Data Analytics, Blade Templates, Scraping, eCommerce, Back-end Development, Large Language Models (LLMs), MERN Stack, CTO, Bots, Cloud Infrastructure, Full-stack Development, Reddit, Google Drive, Integration, Content Management Systems (CMS), API Integration, Google Cloud Functions, Trading, TradingView, Cryptocurrency, Prompt Engineering, Gmail, Email, SDK Development, SDKs, Serverless, Pinecone, Poetry, Computer Networking, Datagram Transport Layer Security (DTLS), Software Engineering, Software Architecture, Navigation, Electric Vehicles, Fivetran, Identity & Access Management (IAM), OpenID Connect (OIDC), Duende, SAML-auth, SecOps, Mobile App Development, Advisory, Leadership, Scalability, Technical Leadership, Startups, Coaching, Engineering, Process Development, Web Scalability, Google Ads, Google Tag Manager, Google Analytics 4, Office 365, PWA, Progressive Web Applications (PWA), Gemini API, DNS, htaccess, GoDaddy, SEO Tools, Hardware, Low-level Programming, USB, MDM, Jamf, Mobile Device Management (MDM), Fintech, Profiling, betting software, Dynamic Load Balancing, Plugins, PKI, LangChain, DDS, Algorithmic Trading, PDF Scraping, Midjourney, Strapi, Web3, Analysis, Dashboards, AI Website Builders, Buffer Management, expressif, Bluetooth, Firmware

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