Jia Jun Koh, Developer in Kuala Lumpur Federal Territory of Kuala Lumpur, Malaysia
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Jia Jun Koh

Verified Expert  in Engineering

Back-end Developer

Location
Kuala Lumpur Federal Territory of Kuala Lumpur, Malaysia
Toptal Member Since
December 2, 2021

Jia Jun is a self-driven tech enthusiast specializing in back-end developments using Go, Python, and Node.js. He enjoys writing automation scripts and building CI/CD pipeline extensions to ship software safely and quickly. Jia Jun is also a team player who believes codes that others can easily understand are the best. He is particularly interested in leveraging his skills and expertise in Go in scalable and distributed systems where good code and architecture matter.

Portfolio

Knockaway Inc
PostgreSQL, Go, OpenAPI, GraphQL, APIs, REST APIs, CQRS, EventStore, Salesforce...
Rain Technologies Inc.
REST APIs, Back-end Development, Go, SQL, Back-end Performance, OAuth, React
Seek Asia
Go, TypeScript, Buildkite, Amazon Web Services (AWS), Docker, Datadog, DevOps...

Experience

Availability

Part-time

Preferred Environment

Go, Google Cloud Platform (GCP), Docker, Firebase, TypeScript, Node.js, Python, Serverless Architecture, Terraform

The most amazing...

...A/B test tool I've helped develop from scratch allows the easier and faster creation of experiments.

Work Experience

Senior Go Developer

2022 - 2023
Knockaway Inc
  • Developed a CQRS system that takes in CDC input from Salesforce and aggregates it into views. This system ensures consistency and reduces time in developing alternative solutions to re-sync data across different sources.
  • Initiated and implemented monitoring adhering to OpenTelemetry specifications.
  • Moved vendor-specific monitoring tools (Datadog Agent) to vendor-agnostic tools (OpenTelemetry Collector, Fluent Bit), allowing dependency on vendors and better adhering to open standards.
  • Created workflow engine prototype using Temporal with workers in different programming languages, including TypeScript and Go, allowing others to contribute to the project without needing to learn a new language.
  • Designed GraphQL system to pull events aggregated from SalesForce CDC events.
Technologies: PostgreSQL, Go, OpenAPI, GraphQL, APIs, REST APIs, CQRS, EventStore, Salesforce, Node.js, Temporal, Workflow, OpenTelemetry, TypeScript

Senior Back-end Engineer

2021 - 2022
Rain Technologies Inc.
  • Developed and maintained RPCs and API gateways to keep services decoupled, improving developer productivity and test coverage. Asynchronously saved requests and events to S3 and DynamoDB for analytics and debugging purposes.
  • Led and designed a service written in an idempotent manner with scaleable serverless stacks for 3rd-party integrations (e.g., WhatsApp).
  • Helped coordinate database migration using a versioning tool (e.g., Goose) to keep the consistency of local, development, staging, and production environments.
  • Initiated and introduced Datadog log archives and rehydration.
Technologies: REST APIs, Back-end Development, Go, SQL, Back-end Performance, OAuth, React

Software Engineer

2020 - 2022
Seek Asia
  • Introduced and co-authored dependency injection pattern boilerplate that reduced the time for contributors to less than two days.
  • Created a reusable CI module that enabled other developers to collect metrics and integrate 3rd-party services, including Datadog, Snyk, and Veracode, with minimal setup.
  • Integrated monitoring and alerts to improve legacy service stability, reducing undetected downtime by more than 50%.
Technologies: Go, TypeScript, Buildkite, Amazon Web Services (AWS), Docker, Datadog, DevOps, Terraform, Node.js

Software Engineer

2019 - 2020
TribeHired
  • Introduced and created a data pipeline using Apache Beam to extract exchangeable image file format (EXIF) metadata of thousands of images in an auto-scaling manner.
  • Created support for an auto-assignment service with custom configurable rules, including a round-robin load balance.
  • Worked with multiple vendors and integrated payment service providers to the system to support real-time multi-currency payments.
Technologies: Node.js, Angular, Kubernetes, Docker, MySQL, GitLab CI/CD, TypeScript, Apache Beam, Google Cloud Platform (GCP), Go, MongoDB, Sentry, SQL, PostgreSQL

Software Engineer

2018 - 2019
AirAsia Group Berhad
  • Worked on developing in-house A/B test tools that enabled developers to create experiments faster as well as develop and release more than 50 experiments.
  • Helped build a data pipeline using Apache Airflow to employ a machine learning model that annotated net promoter score (NPS) feedback and saved at least 100 hours of labor per month.
  • Initiated the decision to move Google Maps to Apple MapKit to support users from China. Helped develop the very first version of the WeChat Mini-Program.
Technologies: Go, Docker, Angular, React, Python, Node.js, Google Cloud Platform (GCP), GitLab CI/CD

Software Developer

2017 - 2018
Solution Engineering Sdn Bhd
  • Developed a supervisory control and data acquisition (SCADA) system for electrical substations in rural areas with limited internet bandwidth constraints.
  • Built an SMS alarm engine using a GSM modem and information security management system (ISMS) service to enable users to retrieve real-time data through SMS.
  • Built a data infrastructure to collect more than 100 different real-time metrics from the database and predict the efficiency and ROI of electrical substations.
Technologies: C#, JavaScript, Microsoft Azure

Smart Sheet

This sheet is an easy-to-use service that utilizes a spreadsheet as a database to help automate tedious processes, including updating the configuration of RabbitMQ, creating cards for Trello boards, and as a stock management system.

Car Park Management System

This complete end-to-end parking solution from a gate control to the cashier was developed using Arduino, Raspberry Pi, Vue.js, and Node.js. In collaboration with two other colleagues, I created the whole solution in three months and shipped it to multiple paid car park shopping malls and condominiums.

Instastalk

https://pypi.org/project/instastalk/
Instastalk is a Python library that scrapes through Instagram to download stories and posts locally through API requests without using any WebDrivers. It supports login for private users with a caching and time-out mechanism to avoid hitting the rate limit imposed by Instagram.

Sonderbase — Travel Blog

https://sonderbase.com/
A travel blog platform that primarily targets text-based content. It leverages cloud storage and its CDN service to reduce costs and latency. It uses a modern WYSIWYG editor (Tiptap) to provide a friendly UI and UX. Its SEO-centric nature also enables some of its content to rank top 10 on Google consistently.

Wonderplan | AI-generated Itineraries

https://wonderplan.ai/
Wonderplan is an AI itinerary planning platform that enables users to generate itineraries in only a matter of a few clicks.

I worked as a back-end developer on the project, developing performant APIs using gRPC and REST. The application is Bootstrapped using Kratos and built in a stateless manner and adhering to standard domain-driven design (DDD) practice. Certain states passed through GCS. A customized temporal version was adopted to manage reliable and robust workflows to generate itineraries through an OpenAI API. In-house proxy and round-robin strategies are developed to overcome rate limits imposed by OpenAI.

Languages

Go, Python, JavaScript, TypeScript, C#, SQL, GraphQL

Libraries/APIs

Node.js, React, Vue, TensorFlow, Protobuf, REST APIs, OpenAPI

Paradigms

Serverless Architecture, Agile, DevOps, Agile Project Management, CQRS

Platforms

Google Cloud Platform (GCP), Docker, Firebase, Buildkite, Amazon Web Services (AWS), Kubernetes, Arduino, Raspberry Pi, Salesforce

Tools

Apache Beam, Spreadsheets, Terraform, GitLab CI/CD, Sentry, Grafana, CircleCI, Firebase Authentication

Frameworks

Angular, gRPC, Gorm

Storage

Datadog, MySQL, MongoDB, PostgreSQL, MySQL/MariaDB, CockroachDB, EventStore

Other

Microsoft Azure, Machine Learning, Google Cloud Machine Learning, SaaS, Web Scraping, OpenTelemetry, Serverless, Content Delivery Networks (CDN), Meilisearch, Temporal, Kratos, Atlas, Back-end Development, Back-end Performance, OAuth, ChatGPT, OpenAI, APIs, Workflow

MAY 2021 - PRESENT

ICAgile Certified Professional

ICAgile

NOVEMBER 2018 - PRESENT

Machine Learning Immersion – Advanced Solution Lab

Google Cloud

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