Jun Yoon, Developer in Sydney, Australia

Jun Yoon

Software Developer

Sydney, Australia
Toptal Member Since
March 5, 2020

Jun is a full-stack engineer with scrum master experience. He studied medicine before switching careers and never looked back! He has six years of full-stack experience using Java, Node.js, JavaScript, and TypeScript throughout various domains, including healthcare, online advertising, networking, and eCommerce.

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Amazon Web Services (AWS)
Amazon Web Services (AWS), React, Node.js, Java, TypeScript
Phocas Software
Amazon DynamoDB, AWS Lambda, Vert.x, Java, GraphQL, TypeScript, Redux, React
Comrad Medical Systems
Redis, Docker, Python, JavaScript, TypeScript, Redux, React, Gradle, Spring...


Sydney, Australia



Preferred Environment

Slack, Jira, IntelliJ, Git, GitHub, WebStorm, Notion

The most amazing...

...things I've built were a mobile first health clinic app, an Airbnb clone, and a time-critical GDPR feature for an ad platform using a microservice architecture.

Work Experience

2020 - PRESENT

Software Development Engineer 2

Amazon Web Services (AWS)
  • Worked as a front-end engineer for Stealth Product yet to be released by Amazon. The technologies used were: React, TypeScript, Node.js, AWS, and AWS-CDK.
  • Optimized React and Redux application to perform 2,000x faster when loading larger payloads.
  • Refactored Java integration tests to run on realistic environments to increase the safety of deployments.
  • Maintained and refactored feature work for distributed back-end network deployment software.
Technologies: Amazon Web Services (AWS), React, Node.js, Java, TypeScript
2020 - 2020

Senior Full-stack Developer

Phocas Software
  • Wrote a web application in Google Sheets style to be used for business accounting and forecasting.
  • Refactored a React application for better performance by moving from State into Redux and adding memoization where appropriate.
  • Mentored junior developers on React best practices through pair programming sessions.
Technologies: Amazon DynamoDB, AWS Lambda, Vert.x, Java, GraphQL, TypeScript, Redux, React
2019 - 2020

Full-stack Engineer

Comrad Medical Systems
  • Digitized paper forms as web apps available on both desktop and mobile to enable patients and health professionals to seamlessly access health data.
  • Retrofitted authorization across Spring and Dropwizard Java back end.
  • Fixed a concurrency JWT refresh bug in express servers using Node.js.
  • Rewrote the web-based app in TypeScript to decrease bugs and increase developer productivity and happiness.
  • Improved the deployment pipeline cycle time and added SonarLint to developer processes to improve the quality of the codebase.
Technologies: Redis, Docker, Python, JavaScript, TypeScript, Redux, React, Gradle, Spring, Java
2017 - 2019

Software Engineer | Scrum Master

Stroër Labs
  • Implemented GDPR compliance changes through the entire ad delivery stack, from JavaScript coding to bidding and auditing.
  • Enabled publishers to choose the ads to show on their websites using a filter as well as to track results through reporting tools.
  • Drove cultural change as a scrum master to adopt more open communication and upfront risk management within an environment of team safety.
Technologies: Amazon Web Services (AWS), PostgreSQL, Citus, ActiveMQ, Apache Kafka, Docker, Python, JavaScript, JDBC, Spring, Java
2015 - 2017

Full-stack Developer

Orion Health
  • Developed features that empower health professionals to manage their patient's list of problems and medications.
  • Brought use of Docker for fast dev/test environment setups to the team.
  • Judged and gave feedback on an internal hackathon used for graduate recruitment.
Technologies: Docker, Selenium, React, Sass, YUI, JavaScript, Apache Maven, Hibernate, Spring, Java


Google Sheets Clone

Implemented web app, which was used as a specialized Google Sheets clone with extra niche features. I further identified performance issues around using Redux and React hooks and migrated to use React Window (virtualized DOM) to improve app responsiveness and optimize GraphQL queries.

Property Rental Web App

Full-stack web application using React-Redux Typescript front end and Java Spring back end that used Google Maps and Google Places APIs to enable viewing and managing property rentals for both renters and property managers. Optimized and cached queries to Google places APIs to reduce costs of calling the API (legally as in the Google T&Cs).

Health Clinic App

This React Redux mobile-first app was used inside health clinics to help patients and clinicians communicate and check-in to the clinic. I re-wrote the base application in TypeScript to detect bugs early on and reduce technical debt in the process as well as fixing various back-end security issues. The back ends included a Node.js, Java, and Springboot stack.



Java, JavaScript, TypeScript, SQL, HTML, CSS, GraphQL, Sass, Python, Kotlin


Express.js, MUI (Material UI), Spring, Redux, Hibernate, Selenium, Vert.x, Hadoop, Spark


Node.js, React, React Redux, JDBC, YUI, Google Maps, Facebook Login, Google APIs, Facebook API, Puppeteer


Test-driven Development (TDD), Agile Software Development, Concurrent Programming, Functional Programming, Reactive Programming


Docker, AWS Lambda, Amazon Web Services (AWS), Apache Kafka, Kubernetes


PostgreSQL, Amazon DynamoDB, Redis, Couchbase, MongoDB


Citus, Apache Maven, Gradle, Java Concurrency, REST Assured, Git, IntelliJ, Jira, Slack, GitHub, ActiveMQ, Docker Compose, Jenkins, WebStorm, Notion


Distributed Software, Apollo, Google Login, GoCD


2019 - 2019

Bachelor's Degree in Health Sciences

University of Otago - Dunedin, New Zealand

2014 - 2015

Diploma in Advanced Software Development

Whitecliffe - Technology & Innovation - Christchurch, New Zealand

2009 - 2013

Bachelor's Degree in Medicine and Surgery

University of Otago - Dunedin, New Zealand