Kai Wa Chan, Software Developer in Hong Kong, Hong Kong
Kai Wa Chan

Software Developer in Hong Kong, Hong Kong

Member since December 29, 2021
Kai is a product-focused Java back-end engineer and test enthusiast with experience in the payments and banking industry, working on mission-critical systems. At Goldman Sachs, he designed and built Kafka-based event-driven microservices to decouple lengthy business workflows, reducing onboarding time from months to ten minutes. Kai produces production-ready solutions that are functional, testable, observable, maintainable, extendable, and scalable.
Kai is now available for hire


  • Freelance
    Java, AWS, PostgreSQL, Spring Boot, Angular, Message Queues, Play Framework...
  • Goldman Sachs
    Spring Boot, Amazon Web Services (AWS), AWS, JUnit, Microservices, Java...
  • The Hut Group
    Java, Spring Boot, ActiveMQ, Microsoft SQL Server, SQL, Maven, Selenium...



Hong Kong, Hong Kong



Preferred Environment

MacOS, Windows, Git, IntelliJ IDEA

The most amazing...

...tool I've worked on is an eCommerce payment system that runs 24/7 and transacted half a million GBP sales during Black Friday in 2018.


  • Software Contractor

    2021 - PRESENT
    • Built the lease and ledger data pipeline by Spring Boot and AWS SQS to sync data from and to the third party to externalize the payment service.
    • Refactored and repurposed the UI-coupled onboarding payment service to support ongoing rent payments.
    • Completed remaining features and bug fixes to launch Plaid and Dwolla ACH payment integration to production, allowing successful rent and deposit onboarding payments.
    • Focused mainly on Java back-end development and built feature enhancements on the front end using Angular and React.
    Technologies: Java, AWS, PostgreSQL, Spring Boot, Angular, Message Queues, Play Framework, Spring Data JPA, gRPC, Amazon SQS, Non-blocking I/O
  • Associate (Software Engineer - Transaction Banking)

    2019 - 2021
    Goldman Sachs
    • Built a solution to support API and UI-driven onboarding processes to Stripe Treasury banking as a service (BaaS).
    • Designed and built Kafka-based event-driven microservices to decouple lengthy business workflows, which reduced onboarding time from months to ten minutes.
    • Designed and built the Camunda maker-checker workflow library and standardized the process.
    • Designed and built the Camunda workflow library, handling and monitoring asynchronous acknowledgments.
    • Established a behavioral testing practice and regression tool to reduce manual testing effort.
    • Researched the feasibility of a MongoDB client-side field-level encryption with Spring-data-MongoDB integration.
    Technologies: Spring Boot, Amazon Web Services (AWS), AWS, JUnit, Microservices, Java, Apache Kafka, NoSQL, GitLab, RESTful APIs, Message Queues, Terraform, MongoDB, Cucumber, REST Assured, java11, AWS ECS, Camunda BPM, Maven, Digital Banking, Scrum, Spring, Databases, HashiCorp, CI/CD Pipelines, API Development
  • Software Engineer (Payments Platform)

    2017 - 2019
    The Hut Group
    • Designed and built API to convert custom rule expressions to trigger fraud measures (3DS, CV2) for card payment.
    • Assisted new card provider and payment 3DS 1.0 integration to enable direct card payment for specific sites to reduce around 2% transaction cost and reduce chargebacks.
    • Migrated ApplePay payment to another provider to align with the provider migration.
    • Brokedown and rewrote parts of a monolith toward microservices architecture to support future scaling and SaaS.
    • Maintained internal payments tool UI (payment method configuration and auditing) with AngularJS and Thymeleaf.
    Technologies: Java, Spring Boot, ActiveMQ, Microsoft SQL Server, SQL, Maven, Selenium, WireMock, Payment APIs, Card Payments, Git, Kanban, Kibana, Grafana, Test-driven Development (TDD), JUnit, Mockito, AngularJS, Jenkins, REST APIs, RESTful APIs, Message Queues, JSON, Spring JDBC


  • Client Onboarding | Transaction Banking

    This is a digital-first corporate banking-as-a-service (BaaS) platform built from scratch. I built solutions that revolutionized the traditional onboarding and account opening experience, which shortened these processes' time to minutes from the industry standard of months. This was achieved by supporting external clients (partners) and internal operations to perform self-service driven by API and UI.

  • Payments | eCommerce

    As part of the payment team, I was in charge of payment methods and providers' integrations such as card, Apple Pay, Alipay, WeChat Pay, and Google Pay. Apart from an integration perspective, achieving high availability, fault-tolerance, scalability, and providing observability to both the business and team were also my main deliverables.

  • ACH Payment Integration | Residential Property Leasing

    This is a minimum viable product to support one-time residential lease payment on web or mobile platforms. I joined the team in the late waterfall stage. I was in charge of resolving bugs and missing scenarios on Plaid authentication and Dwolla ACH and balance transfer.


  • Languages

    Java, SQL
  • Frameworks

    Spring Boot, JUnit, Mockito, Swagger, Spring JDBC, Selenium, AngularJS, Play, gRPC, Angular, Play Framework, Spring
  • Tools

    WireMock, Maven, GitLab, Amazon SQS, Git, IntelliJ IDEA, GitLab CI/CD, ActiveMQ, Kibana, Grafana, Camunda BPM, Jenkins, Terraform, Cucumber, REST Assured, AWS ECS, HashiCorp
  • Paradigms

    Object-oriented Programming (OOP), REST, Test-driven Development (TDD), Microservices, Kanban, Scrum
  • Other

    Back-end, AWS, Workflow, Payment APIs, Message Queues, Networks, Card Payments, RESTful APIs, Finance, java11, Digital Banking, CI/CD Pipelines, Non-blocking I/O
  • Platforms

    Amazon Web Services (AWS), Apache Kafka, MacOS, Windows
  • Storage

    NoSQL, Spring Data JPA, Microsoft SQL Server, PostgreSQL, JSON, MongoDB, Databases
  • Libraries/APIs

    PostgREST, REST APIs, API Development


  • Bachelor's Degree in Computer Science
    2015 - 2017
    Cardiff University - Cardiff, Wales, UK

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