Hao is available for hire

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

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...

Uber

C++, Java, Go, Node.js, Cloudflare, Architecture, Logging, WordPress...

Experience

Java - 10 years C++ - 10 years Distributed Systems - 10 years Python - 9 years Node.js - 8 years Ruby on Rails (RoR) - 8 years Go - 8 years Machine Learning - 7 years

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

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

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, 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

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, 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

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

Principal Engineer

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

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, 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

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, 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

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, GDB, Boost, GitHub, Back-end Development, Google Cloud, Integration

Experience

Uber | Global Service Platforms

http://www.uber.com

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

http://www.roblox

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.

Skills

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

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, Angular

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, Vue, Python API

Tools

Logging, Amazon Elastic Container Service (Amazon ECS), AWS Key Management Service (KMS), Terraform, HashiCorp, Cloud Dataflow, Git, GDB, CMake, GitHub, RabbitMQ, ChatGPT, Google Analytics, Docker Hub, BigQuery, Cron, Android Studio, Expo, Azure Active Directory B2C (ADB2C), Hashistack, Keycloak, Apache Beam, AWS IAM

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

Platforms

Linux, Apache Kafka, Docker, WordPress, Amazon Web Services (AWS), Google Cloud Platform (GCP), Firebase, BigCommerce, DigitalOcean, Heroku, Mobile, iOS, Android, Mapbox, Azure, Blockchain, Kubernetes, Windows, Neto

Storage

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

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, Dynamic Load Balancing, Plugins, PKI, GPT, LangChain, DDS, Algorithmic Trading, PDF Scraping, Midjourney, Strapi, Web3, Analysis, Dashboards

Education

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

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