Tao Zhang, Developer in Kirkland, WA, United States
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Tao Zhang

Verified Expert  in Engineering

Software Developer

Kirkland, WA, United States
Toptal Member Since
May 6, 2015

Tao is a senior full-stack developer and architect who worked on over 14 million lines of code on large-scale, real-time acquisition software projects. He primarily focused on the back end for more than 11 years. Tao's expertise is mainly in C++, C#, Java, Python web development, performance optimization, and troubleshooting in Azure and AWS.


Go, Kubernetes, Oracle DBaaS, REST APIs, API Integration, SQL, APIs...
JPMorgan Chase
Amazon Web Services (AWS), Performance, Spring 5, Postman, JSON, Web API...
Software Architecture, Postman, JSON, ASP.NET Core 2, Moq, TFS...




Preferred Environment

Amazon Web Services (AWS), Spring, Azure, ASP.NET, Python, Java, C++, C#

The most amazing...

...web service I've created was for a large-scale project which automated log analysis and problem troubleshooting workflow.

Work Experience

Principle Software Engineer

2021 - PRESENT
  • Developed a highly available, high performance and highly scalable REST API service in Oracle OCI using Go language in the back end to provide authorization service for internal client.
  • Developed and maintained CI/CD pipelines build script to deploy REST API services in Kubernetes pods running in Oracle OCI and troubleshooting with Kubernetes CLI.
  • Designed async API to support bulk operation for clients to import or upload huge amounts of data to our authorization service and stored data to Oracle DB.
Technologies: Go, Kubernetes, Oracle DBaaS, REST APIs, API Integration, SQL, APIs, Oracle PL/SQL, Oracle, Spring Boot, Object-oriented Programming (OOP), Automation, Back-end Architecture, DB, Architecture, Databases, Leadership, Agile, Git, Linux, Microservices, SDKs, Regular Expressions, RESTful Services

Senior Software Engineer

2020 - 2021
JPMorgan Chase
  • Provided a scalable, highly available, and low latency data transformation web service in a public and private cloud with a Java back end.
  • Worked on performance enhancement and troubleshooting to better support more than 1000 TPS during peak time.
  • Built-up a CI/CD pipeline to generate metrics data for every build, unit test/integration test execution, deployment, and more. Also, achieved zero downtime during every deployment.
Technologies: Amazon Web Services (AWS), Performance, Spring 5, Postman, JSON, Web API, Design Patterns, HTTP REST, JavaScript, Node.js, Back-end, REST APIs, Apache JMeter, Cassandra, Jenkins, Python, Java, XML, SQL, Bootstrap, Spring Boot, Apache Kafka, Object-oriented Programming (OOP), React, Back-end Architecture, DB, Architecture, Databases, Leadership, Agile, AWS Lambda, Git, Linux, Microservices, SDKs, RESTful Services

Senior Software Engineer

2019 - 2020
  • Developed a web service for a mobile payments app in .NET/.Net Core and C# running in Azure. Utilized SQL Server DB, Azure Cosmos DB, Redis Cache, and In-memory cache as a data storage strategy to achieve the best performance.
  • Applied the blue-green deployment strategy in Azure to ensure zero downtime during app service deployment, web jobs, azure functions, etc.
  • Created web jobs in Azure to communicate with different payment hosts by different payment types, such as Google Pay, Apple Pay, Samsung Pay, or Chase Pay.
  • Used C# to create a new payment workflow with Worldpay. Got payment info from the Service Bus topic and packed them into ISO 8583 message format, sent to WorldPay server, and returned transaction result as Service Bus message.
  • Implemented in-memory cache with TTL in C#. An LRU cache can get data from SQL Server and Cosmos DB. It also supports REST API to access the cache.
  • Used Service Bus to support event-driven workflow to combine different web jobs to finish payment workflow. Each web job will be a consumer and producer of a specific Service Bus message.
  • Worked on a data analysis project which tries to gather performance metrics data by different payment workflows. Data came from Cosmos DB with indexes created to get better performance.
Technologies: Software Architecture, Postman, JSON, ASP.NET Core 2, Moq, TFS, Chase Paymentech, ISO 8583, Worldpay, Google Pay, Microsoft SQL Server, .NET Core, .NET, Visual Studio, Oracle Service Bus (OSB), Service, Azure Cosmos DB, C#, ASP.NET, XML, XML Parsing, Fintech, REST APIs, API Integration, SQL, APIs, Bootstrap, Azure, Object-oriented Programming (OOP), C#.NET, Back-end Architecture, DB, Architecture, Payment APIs, Databases, Leadership, Agile, SQL Server 2012, Microservices, Regular Expressions, RESTful Services


2019 - 2019
Palmetto Wood Shop, LLC
  • Extracted Excel data and processed it using VBA script.
  • Utilized CorelDRAW API to automate interaction with CorelDRAW UI. Integrated CorelDRAW and ShipStation.
  • Used hashmaps, collections, arrays, and data structures to process and convert data from ShipStation to CorelDRAW.
Technologies: CorelDRAW, Microsoft Excel, Visual Basic for Applications (VBA), CSS

Senior Software Engineer

2007 - 2019
  • Redesigned data structure, re-architected software, and introduced parallel programming in back end to improve the performance of web services and desktop apps. Improved performance from 30%-80% in large scale real tie acquisition system.
  • Set up the CI system to improve development efficiency for a large population of the community. Improved the development life cycle time from 3-7 hours to 10-60 minutes which save a lot of money for the projects.
  • Worked as one of the authors to write C++ and C# coding standards for projects. Around 150 developers all over the world followed this coding standard in daily work and code review session.
  • Created web service to host an automatic log file analysis and dump file analysis. Promoted the project troubleshooting and monitoring to higher level and saved a lot of money for the project.
  • Introduced the static code analysis tool Coverity to project for C++, C# and Java. Has been integrated to CI system in 2009 and still acts as one of the most important metrics data to measure code quality.
  • Worked as a full-stack developer to create REST API with Java and Node.js/JavaScript to support real-time monitoring and alarm. Created a service that provides a good view about healthy status of all apps running in either cloud or desktop.
  • Implemented tool control system via Socket in C++. Controled behavior of hardware by sending a command to hardware and it also read messages sent from hardware to know the real-time status of hardware.
  • Used Amazon Lambda to host a small web service to maintain hardware inventory info. Compared Lambda and EC2 and chose Lambda by its lower cost and fast deployment. Done in Java.
Technologies: Performance, Software Architecture, MySQL, Web API, TFS, Google Test, Standard Template Library (STL), Design Patterns, IIS, JavaScript, .NET, JSON, Windows Presentation Foundation (WPF), ASP.NET, Moq, Docker, Microsoft SQL Server, COM, Python, Node.js, Java, C++, C#, Visual Studio, XML, XML Parsing, APIs, Azure, .NET Core, Object-oriented Programming (OOP), C#.NET, Automation, React, HTML, Back-end Architecture, DB, Architecture, Databases, Leadership, Agile, SQL Server 2012, Git, SDKs, C#.NET WinForms, Regular Expressions, Sockets, RESTful Services

Senior Software Developer

2004 - 2007
Nortel Networks
  • Designed an Oracle database and developed stored procedures.
  • Programmed in Java to add new features for the network and telecommunication device management system.
  • Utilized Solaris/Linux commands and Bash shell as a small tool in daily development.
  • Programmed in C++ to create an interface between hardware and the Java application.
  • Used Eclipse as an IDE to do the coding work for C++ and Java.
Technologies: Eclipse IDE, IBM Rational Rose, Unix Shell Scripting, Design Patterns, Solaris, C++, Java, Software Development, Oracle PL/SQL, .NET Core, Object-oriented Programming (OOP), CTI, Telephony, SIP

Senior Software Developer

2001 - 2004
  • Designed MySQL database tables and developed stored procedures to support a medical remote diagnostic system.
  • Developed ASP web pages with JavaScript to provide query and statistic function.
  • Developed COM objects as back-end or business logic layer in C++. Those COM objects acted as a small service to combine the whole workflow together.
  • Created IP phone functionality based on the H.323 protocol. Integrated with high efficient compression and decompression algorithm. Also integrated with the echo elimination algorithm.
  • Created a C++ program based on different medical image formats such as CT and MRI.
  • Created automatically fax module by integrating it with hardware in C++. Converted a text into a TIFF format file, sent it to hardware, and to the target fax machine.
Technologies: MySQL, Standard Template Library (STL), IIS, C++, JavaScript, ASP.NET, Software Development, Object-oriented Programming (OOP), DB, App Installation

CI System for a Large-scale Project

I have been working with a large scale software system that has a total of 14 million lines of code (C#/C++) for 11 years. It used to take 8-10 hours to build and generate the installation kit or deploy it to the cloud. With the old baseline build, it could only generate one build and one kit per day.

We built the CI (continuous integration) system in Python mainly and also used Powershell, Jenkins, and other technologies to implement automated processes in the development cycle.  After setting up the CI system, the average build time is about an hour and installation kit generation/deployment takes about 1-1.5 hours.

We also introduced many code metrics such as compile warnings, code complexity, and unit test coverage into the CI system. In addition, the CI system also helps to run all kinds of automation testing and generate reports. The CI system improved development efficiency for about 200 developers, QAs, and managers.

TDD Applied to a Large Legacy C++ Codebase

I redesigned many complicated classes in a large-scale C++ codebase following different design patterns, such as singleton, factory method, composite, adapter, or observer. The C++ codebase was refactored to make it testable by extracting to interfaces. I used GTest/Gmock provided by Google to test our legacy C++ class. 

Automated Workflow Analysis and Troubleshooting

As a large-scale real-time acquisition system, we set up a central place to store logs, performance data, dump files, etc., which are collected from different desktops or public cloud deployments.
We developed a web service to provide automated processes for different purposes, such as log file analysis to find the most popular tool string combination, performance data analysis to find out potential performance bottlenecks; dump file analysis to find the root cause of a crash or exception. We use C# with .NET Core and Python to develop the back end and Node.js and JavaScript to develop the front end.
SQL Server and Cosmos DB NoSQL as DB were implemented for data storage, and Redis cache and memory cache as another layer of data storage to achieve better performance. This web service was deployed to Azure.

Payment Workflow API

I designed and implemented the REST APIs/endpoints for a payment workflow serving as an e-payment web service or serving a mobile app. The web service runs in Azure and communicates with different payment service providers to finish payments. It is built on top of C#/ASP.NET/.NET Core. It utilized different layers of data storage: SQL Server, Cosmos, Redis Cache, and an in-memory cache in different stages of the whole workflow to achieve the best performance.

We built different web pages with Node.js and Angular. Those web pages can serve developer troubleshooting purposes, statistics, and reporting purposes for managers and operation stuffers, testing REST APIs and making demos for clients, etc.

Data Interpretation and Conversion

I developed a web service to provide different format files, such as DLis, or PDF, as the client requires deliveries of a large, real-time acquisition system. I used Java and Python as back-end coding languages to support a web service running in AWS. For the database, I used Cassandra and Amazon S3 as data storage. Further, I used Node.js for the front end to set up a simple UI and perform API testing. TDD is applied throughout the whole lifecycle of the project.

Telecommunication Device Management System

I built a 3G device management system running in Unix for Nortel Networks. That system was developed by Java together with a small part of a C++ component. The C++ code mainly communicates with 3G devices via socket connection based on a special protocol.
Java code builds whole systems based on MVC, including UI, business logic, and data models. I used JNI to connect Java MVC parts with C++ components to get and set the configuration of 3G devices from the UI down to the hardware.

.NET Core REST API Server Development

I rewrote a Java-based REST API service using C#/.NET Core. This REST API server performs the following things:
• Receive XML requests from a financial organization
• Deserialize the raw XML request to a specific data model based on different request types in XML
• Apply different logic to convert data models in different workflows
• Serialize the final data model to XML and send it back

Excel Add-ins Development

The client produces metrology software. The software allows for gathering precision measurements and allows its customers to test their measurement equipment to see if it is reliable. The client needs to create an Excel add-in from scratch that takes various inputs and then creates the Excel sheet template dynamically.

Call Center Project

Created a call center platform to support different industries, providing the following common functionalities:

1. An IVR system integrated with Nortel PBX system to support the configurable automatic voice response system to provide information query, booking, etc.
2. An automatic fax system.
3. IP phone call.

Java and Spring Boot REST Service

I worked in the data security department to provide tokenization and key management service to support large volume transactions for internal customers in the bank. I built up a highly scalable, highly available, and high-performance web service that deploys to AWS and a private cloud (based on CloudFoundry) with Java and Spring Boot as the back end, Cassandra and DynamoDB as data storage, and Apache Kafka as a message queue. I also mentored new team members to catch up on project and technical stacks quickly.
1992 - 1996

Bachelor's Degree in Mathematics and Application Software

Jilin University - Changchun, Jilin, China


Certified Developer – Associate Certification Preparation for AWS

Cloud Academy


Google Cloud Platform Fundamentals: Core Infrastructure

Google Cloud


Machine Learning

Stanford University

MAY 2004 - MAY 2014

Java Certified Programmer



Node.js, REST APIs, Sockets, Standard Template Library (STL), Moq, Web API, React, Google APIs, PyTorch


Apache JMeter, WinDbg, Visual Studio, C#.NET WinForms, Jenkins, TFS, Git, Postman, Microsoft Excel, CorelDRAW, Eclipse IDE, Mercurial, IBM Rational Rose, GitLab, cURL Command Line Tool, Oracle DBaaS, Kafka Streams


.NET Core, .NET, Google Test, Spring Boot, ASP.NET, Windows Presentation Foundation (WPF), Windows PowerShell, ASP.NET Core 2, ASP.NET MVC, Spring, Spring 5, Bootstrap


JavaScript, Java, C#, C++, Python, Go, C#.NET, XML, SQL, CSS, HTML, Visual Basic for Applications (VBA), XSD, DYNAMO, Python 3


Test-driven Development (TDD), Socket Programming, Object-oriented Programming (OOP), Automation, Back-end Architecture, Microservices, Design Patterns, Agile


Windows, Azure, Windows Desktop, AWS Lambda, Amazon Web Services (AWS), Oracle, Linux, Kubernetes, Apache Kafka, Solaris, Docker, Google Cloud Platform (GCP), AWS Cloud Computing Services


Microsoft SQL Server, DB, Databases, Cassandra, MySQL, SQL Server 2012, Azure Cosmos DB, JSON, Redis Cache, XML Parsing, Oracle PL/SQL, Oracle RDBMS, Amazon S3 (AWS S3), NoSQL


Back-end, Performance, IIS, Debugging, COM, Software Development, Memory Leaks, C++ Memory Model, HTTP REST, APIs, CI/CD Pipelines, Cloud Architecture, Architecture, SDKs, RESTful Services, Mobile Payments, Chrome Extensions, Software Architecture, Web Services, Google Pay, Worldpay, ISO 8583, HTTP, HTTPS, Chase Paymentech, Fintech, Serverless, Payment APIs, Leadership, CTI, App Installation, Telephony, SIP, Regular Expressions, Service, Oracle Service Bus (OSB), Unix Shell Scripting, FirstData, Machine Learning, API Integration, Serializer/Deserializer (SerDes), Excel Add-ins, Excel Expert, Office 365

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