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To Hong Hai (Hector)

Backend engineer. I build the services behind payments, logistics and data, in Java and Spring Boot

Email HectorLinkedIn

About

$ cat about.md

Software engineer with 4.5 years delivering production systems across payments, logistics, data analytics and e-commerce. Currently building back-end services for a smart POS platform at EPOS (Ant International). Applies design patterns, microservices architecture and full-stack development to solve real-world problems at scale.

Experience

$ history

  1. 2025.07 → NowJava Backend DeveloperEPOS (Ant International)
    • Developed the Blue Tap refund feature for Malaysia, using idempotency keys, a state machine and reconciliation to prevent double refunds; the POS verifies and forwards transactions to the payment gateway.
    • Automated monthly Malaysian government e-invoice submission with a secure export pipeline and scheduled batch job, using distributed locks and DB constraints to prevent duplicate processing.
    • Collaborated with Product Owners to translate PRDs into production-ready Spring Boot services (PostgreSQL) on Alibaba Cloud, deployed via Jenkins CI/CD with a canary strategy, reducing release risk and enabling nearly zero-downtime roll-outs.
    • Wrote unit and integration tests with JUnit and Mockito across Spring Boot services, and produced sequence diagrams from business requirements to align backend design with stakeholder expectations, improving test coverage and reducing ambiguity during system analysis.
    • Contributed to migrating a legacy Ruby service to Java Spring Boot, reducing server workload by ~30% during peak hours.
    • Used Claude Code in daily development to analyze legacy logic for backward compatibility, do system analysis, and speed up implementation and code review.
    • Java
    • Spring Boot
    • PostgreSQL
    • Alibaba Cloud
    • Redis
    • Distributed systems
    • RocketMQ
    • Claude
  2. 2024.05 → 2025.05LookML Specialist & Lead DeveloperCyberlogitec Vietnam · DDE
    • Established data cleaning and transformation pipelines for analytical reporting, ensuring consistency and accuracy across all business intelligence outputs.
    • Coordinated a team of three developers using SAFe Agile practices, delivering 6+ data models to production within 12 months.
    • LookML
    • Google Looker
    • IBM Cognos
    • SQL
    • Agile (SAFe)
  3. 2024.09 → 2025.04Full-Stack DeveloperCyberlogitec Vietnam · Opus Modernization
    • Built full-stack features using Next.js and NestJS with TypeORM on PostgreSQL, implementing microservices architecture across modernized shipping platform modules, improving data integrity and reducing inter-service coupling.
    • Redefined system functionality against updated service delivery standards using TypeScript across the full stack, enhancing compatibility and reducing technical debt.
    • Next.js
    • NestJS
    • TypeORM
    • TypeScript
    • PostgreSQL
    • Microservices
  4. 2022.03 → 2024.09Java DeveloperCyberlogitec Vietnam · OPUS for Ocean Network Express
    • Developed and maintained REST APIs and business logic for shipping logistics applications with Oracle DB, handling large-scale cargo data for shipping line O.N.E, improving system reliability and processing throughput.
    • Applied structured testing methodologies and code review practices, reducing production bug count and improving code maintainability.
    • Developed and enhanced existing features to meet evolving business requirements while maintaining application reliability and data consistency.
    • Java
    • Spring
    • Spring Data JPA
    • Oracle DB

Stack

$ cat stack.toml

Languages
  • Java
  • TypeScript
  • JavaScript
  • Python
Frameworks
  • Spring Boot
  • NestJS
  • Next.js
  • Node.js
Databases
  • PostgreSQL
  • MySQL
Cloud & infra
  • Alibaba Cloud
  • Docker
  • Jenkins CI/CD
  • Nginx
  • Git
Frontend
  • React
  • Tailwind CSS
Practices
  • Microservices
  • Design patterns (Template Method, Strategy, Command)
  • Unit testing (JUnit, Mockito)
  • Grey / canary deployment
  • Agile / SAFe
AI tools
  • Claude Code
  • Harness
Education
B.Eng. Electrical Engineering TechnologyHCMC University of Technology and Education
Certifications
  • Java Programming Masterclass (Java 11 & 17)Udemy · Tim Buchalka
  • Backend Java DeveloperT3H Institute
  • Google Data Analytics CertificateCoursera
  • EF SET 74/100 · C2 ProficientEF Standard English Test
  • TypeScript: OOP & Essential TrainingLinkedIn Learning
  • DevOps FundamentalsInformatics Center, University of Science

Writing

$ ls ~/blog

  1. How Java Runs: JDK, JRE, JVM, JIT and GCWhat happens between writing a .java file and running it: JDK vs JRE vs JVM, bytecode, the JIT compiler, the five JVM memory areas and the garbage collectors.
  2. Designing a Unique ID Generator for Distributed SystemsFour ways to generate unique IDs across many servers: multi-master replication, UUID, ticket server and Snowflake. What each costs, and why Snowflake fits.
  3. HashMap vs ConcurrentHashMap in JavaThe difference between HashMap and ConcurrentHashMap in Java: how each works inside, thread safety, nulls, and when to use which.
  4. How Computers Store and Manage Time
All posts

Write to Hector

$ mail hector

Based in Ho Chi Minh City, Vietnam, UTC+7. Email and LinkedIn both reach him.

honghai.sg99@gmail.com
Email Hectorlinkedin.com/in/honghaisg