Huy H.

𝗬𝗼𝘂𝗿 𝗦𝗽𝗿𝗶𝗻𝗴 𝗕𝗼𝗼𝘁 𝗔𝗣𝗜 𝗺𝗼𝘃𝗲𝘀 𝗿𝗲𝗮𝗹 𝗺𝗼𝗻𝗲𝘆. 𝗪𝗶𝗹𝗹 𝗶𝘁 𝗵𝗼𝗹𝗱 𝘂𝗻𝗱𝗲𝗿 𝗿𝗲𝗮𝗹 𝗹𝗼𝗮𝗱? I'm a backend engineer who builds and hardens secure APIs and microservices for fintech and payments. 6+ years in Java, Kotlin, and Spring Boot, bank-grade. When money moves through your system, a backend bug isn't cosmetic. It's a failed payment, a stuck loan application, or a 2am page. Most Java backends I get called into look fine in a demo, then crack under real traffic. Endpoints time out, a Kafka consumer silently drops events, retries do nothing, and the tests only cover the happy path. You want someone who has shipped this inside a real bank, not someone learning on your budget. I help fintech teams and SaaS founders ship backends that stay correct and fast when money and auditors are watching. What clients say after working with me: 🏅 "Huy is an excellent engineer. He is fast and highly capable. He understands requirements, asks appropriate questions, and writes great code. Highly recommended." (5.0, long-term backend contract) 🏅 "Huy is an excellent developer and very professional." (5.0, 496-hour Spring Boot contract) I write the code that processes online lending applications at National Australia Bank, so I build to banking standards by habit: secure by default, covered by tests, safe to deploy on a Friday. We're probably a fit if you've caught yourself thinking: 🔑 "Our Spring Boot service works, but I don't trust it with more traffic." 🔑 "We need to add payments, or a new provider, and cannot afford to get it wrong." 🔑 "Our data pipeline is held together with cron jobs and hope." 🔑 "A contractor left us a Java codebase and nobody wants to touch it." Work with me and you'll: 🎉 STOP STRUGGLING with flaky endpoints. I build Spring Boot REST APIs with real error handling, validation, and JUnit coverage, so failures surface before users do. 🎉 Move money safely. I've shipped Paypal, ECPay e-invoicing, and delivery integrations to production. I secure APIs with OAuth2 and AWS Cognito, and build in idempotency and audit logging so money moves are safe to retry and traceable. 🎉 Handle real volume. I build event-driven services on Apache Kafka and Apache Flink with retries and dead-letter handling, so events aren't silently dropped. It's the backbone analytics and AI features run on. 🎉 Not have to hire a backend dev, a DevOps engineer, and a DB specialist and hope they line up. I ship the API, the Docker and AWS deploy, and the Postgres schema as one piece, and I work inside your PR and CI so nothing money-critical merges unreviewed. I started in Java on desktop software, then built an order and payment platform for merchants across Southeast Asia. After a year on the backend of Vietnam's most-used messaging app, I moved into banking, taking lending products to the cloud on Spring Boot and AWS. That path taught me what tutorials skip: how backends fail in production, and how to build so they don't. The numbers behind that: ✅ 6+ years in Java, Spring, and the Spring Boot ecosystem ✅ 𝟭𝟬𝟬% 𝗝𝗼𝗯 𝗦𝘂𝗰𝗰𝗲𝘀𝘀 across 14 jobs and 669 tracked hours on Upwork ✅ $50,000+ earned, including 2 long-term 5.0 contracts worth $36k and $11k ✅ Oracle Certified Associate, Java, plus Upwork's Java Back-End Development certification 🛠️ Tech I build with: ✔ Languages: Java 8, 11, and 17, Kotlin, SQL ✔ Backend: Spring Boot, Spring Framework, Hibernate, RESTful APIs, GraphQL, microservices ✔ Data and streaming: Apache Kafka, Apache Flink, PostgreSQL, MySQL, MongoDB ✔ Cloud and DevOps: AWS, AWS Cognito, Docker, Tomcat, Gradle, Maven, Git ✔ Testing and integrations: JUnit, Mockito, Paypal, ECPay, external REST APIs 📩 Think we might be a fit? Send a short note about your backend and your problem. I'll come back with the first 2 or 3 things I'd check or fix, and an honest read on whether I'm the right fit. I keep a light contract load on purpose, so the projects I take on get real focus.