
Jia Jun Koh
Verified Expert in Engineering
Back-end Developer
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
Experience
- Serverless Architecture - 5 years
- Google Cloud Platform (GCP) - 5 years
- Docker - 5 years
- Go - 5 years
- Python - 5 years
- Amazon Web Services (AWS) - 4 years
- Terraform - 3 years
- TypeScript - 3 years
Availability
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
Go Back-end Developer
Fusang
- Introduced AtlasGo to manage and version database migration in an automated fashion, which reduced the average hour's effort spent manually applying and verifying changes.
- Added open telemetry tracing to the system to enhance observability. Traces and metrics were also used to identify system bottlenecks.
- Developed a cron system, which executes idempotent workflows to guarantee data consistency.
Senior Go Developer
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.
Senior Back-end Engineer
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.
Software Engineer
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%.
Software Engineer
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.
Software Engineer
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.
Software Developer
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.
Experience
Smart Sheet
Car Park Management System
Instastalk
https://pypi.org/project/instastalk/Sonderbase — Travel Blog
https://sonderbase.com/Wonderplan | AI-generated Itineraries
https://wonderplan.ai/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.
Certifications
ICAgile Certified Professional
ICAgile
Machine Learning Immersion – Advanced Solution Lab
Google Cloud
Skills
Libraries/APIs
Node.js, React, Vue, TensorFlow, Protobuf, REST APIs, OpenAPI
Tools
Apache Beam, Spreadsheets, Terraform, GitLab CI/CD, Sentry, Grafana, Meilisearch, CircleCI, Firebase Authentication, ChatGPT, RabbitMQ
Languages
Go, Python, JavaScript, TypeScript, C#, SQL, GraphQL
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, Apache Kafka
Frameworks
Angular, gRPC, Kratos, 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), Temporal, Atlas, Back-end Development, Back-end Performance, OAuth, OpenAI, APIs, Workflow
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