YangYu Song, Developer in Singapore, Singapore
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YangYu Song

Verified Expert  in Engineering

Full-stack Developer

Singapore, Singapore
Toptal Member Since
June 21, 2021

YangYu is a full-stack developer with 6+ years of professional experience focusing on the back end. He has worked in fast-paced startups and big companies with remote teams, such as Grab, Shopee, and PayPal. YangYu is proficient in Go and Ruby on Rails and cares deeply about code quality, readability, and maintainability.


Algorithms, Go, Memcached, Clean Code, Clean Architecture, MySQL, Grafana...
Grab Holdings
Go, ScyllaDB, Amazon Web Services (AWS), SQL, REST, Microservices, Back-end...
90 Seconds
Ruby on Rails (RoR), GraphQL, Amazon Web Services (AWS), Ruby, SQL, REST...




Preferred Environment

Ubuntu, MacOS, Slack, Mattermost, Git, GitHub, GitLab, Jenkins, GitLab CI/CD

The most amazing...

...thing I've migrated is the cache layer of a 200,000 QPS service without any noticeable extra latencies in the API.

Work Experience

Senior Software Engineer

2020 - PRESENT
  • Maintained core user APIs and cache consistency, updated the pipelines, took on-call duties, and handled a 500,000 queries per second (QPS) peak.
  • Led the development of features related to the user's address. Talked to project managers and related stakeholders about product features and design system architecture.
  • Built test cases and lint rules and reported the test coverage on GitLab.
  • Wrote proper documentation about our and others' systems and set up standards for how to write API documentation within our team.
Technologies: Algorithms, Go, Memcached, Clean Code, Clean Architecture, MySQL, Grafana, Prometheus, Apache Kafka, Back-end, Architecture, Docker

Senior Software Engineer

2019 - 2020
Grab Holdings
  • Led the development of an auto-billing service for advertisers, creating the complete service from scratch to production.
  • Spearheaded our service infrastructure and load test internal system. Managed the auto-scaling policy on AWS, ensuring the service met its SLA under a given load.
  • Took on-call duties, answered colleagues' questions, debugged issues, created Jira tickets based on user feedback, and improved monitoring alerts based on incidents.
Technologies: Go, ScyllaDB, Amazon Web Services (AWS), SQL, REST, Microservices, Back-end, Architecture, Docker

Senior Software Engineer

2018 - 2018
90 Seconds
  • Designed and implemented GraphQL API endpoint for different apps. Furthermore, I also improved the GraphQL subscription in the GraphQL-Ruby repository.
  • Upgraded the monolith website from Rails 3.2 to 4.2.
  • Synchronized with the product team to identify the real problem, managed tasks for other back-end engineers, and set up proper Git workflow with Jira and GitLab.
Technologies: Ruby on Rails (RoR), GraphQL, Amazon Web Services (AWS), Ruby, SQL, REST, PostgreSQL, Back-end, Architecture, Docker

Software Engineer

2015 - 2017
  • Developed a customer review module using React and Redux.
  • Built the basic product and voucher logic in Solidus.
  • Designed the listing product attributes and pushed them to Elasticsearch via CronJob.
Technologies: Rails Engines, React, Redux, SQL, REST, Back-end, Architecture

Ad Auto Billing Pipeline

Implemented an auto-billing pipeline in Go, which Grab uses to bill the merchants who use GrabAds. The pipeline aggregates the ingested ad display data and creates the billing records by calling the corresponding services.

I built the entire pipeline from scratch, using AWS Lambda and CloudWatch. It has a test coverage of more than 70% and runs daily for all Southeast Asia countries where Grab operates.

Customer Review Listing Page

Castlery had a customer review listing page with a Ruby on Rails back end serving customer cases, allowing customers to post reviews independently. The front end was a React component initially placed on a Magento eCommerce website.

The company then migrated the website to a Ruby on Rails serving the back-end API and React front-end website. This review component was then integrated with the other components as a complete, single-page application.

Music Notebook

Music Notebook is a notebook for people to upload music and share comments.

I was in charge of building the whole back end, including providing RESTful API, supporting live events via ActionCable, processing the uploaded music via Google Cloud Functions, and monitoring it via Datadog. The app was deployed on Heroku, running in the lowest pricing tier, such as the hobby tier.
2016 - 2018

Master's Degree in Computer Science

National University of Singapore - Singapore

2010 - 2014

Bachelor's Degree in Computer Engineering

National University of Singapore - Singapore


Parallel, Concurrent, and Distributed Programming in Java



Deep Learning



Architecting with Google Compute Engine



Rails Engines, React


Git, Jira, Jenkins, GitLab CI/CD, Grafana


Ruby on Rails (RoR), Redux


Go, Ruby, HTML, SQL, JavaScript, CSS, Java, GraphQL


REST, Microservices, Clean Code, Clean Architecture


Amazon Web Services (AWS), Docker, Ubuntu, Apache Kafka, Google Cloud Engine, Heroku


Databases, Memcached, PostgreSQL, ScyllaDB, MySQL


Back-end, Architecture, Algorithms, Optimization, Migration, Distributed Systems, Cloud Computing, Deep Learning, Concurrency, Compilers, Prometheus

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