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Backend Engineer

Nguyen Quang Vinh

Backend Software Engineer (Java)

Contact: contact@vinhnq.com · vinhnq.com · github.com/Nqvinh7603 · linkedin.com/in/nqvinh76

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Profile

Java Backend Engineer with 3 years of experience, mainly in banking and fintech: digital signature platforms with HSM/PKI and VNeID integration, document automation for Standard Chartered Bank, and the NAPAS ACH interbank payment gateway. Currently the main backend engineer of a multi-tenant SaaS and responsible for production releases of two live platforms.

Skills

Domain
Banking & fintech (digital signature/PKI, interbank payment, payment gateway, document workflow), multi-tenant SaaS
Backend
Java (17, 21), Spring Boot, Spring Security (JWT, OAuth2), Spring Cloud, MyBatis, JPA/Hibernate, QueryDSL, Flyway
Architecture
RESTful API design, microservices, hexagonal architecture, event-driven (Kafka), multi-tenancy, RBAC
Data & messaging
PostgreSQL, MySQL, Oracle, SQL Server, Redis, Apache Kafka
Integrations
Toss Payments, Kakao AlimTalk, OAuth2 social login, PDF signing (PAdES, PKCS#7) with HSM (PKCS#11), Activiti BPMN
DevOps & tools
Docker, Kubernetes, Helm, GitLab CI, GitHub Actions, AWS (ECS Fargate, EKS, RDS, S3, CloudFront), Prometheus, Grafana, Linux (LPI certified), JUnit 5, Mockito, Git

Experience

Wala-ICT · Backend Software Engineer

04/2026 – Present

S-Space · Pilates & fitness studio SaaS

Backend Engineer · Team of 5 · live at s-space.co.kr

  • Maintained and debugged the production AWS environment: VPC with private subnets, ECS Fargate, Multi-AZ RDS, ALB, CloudFront, S3, and Secrets Manager.
  • Handled production releases through GitLab CI → ECR → ECS Fargate as main backend maintainer of the auth, user, and center services.
  • Built a reconciliation job that recovers payments with lost success callbacks and expires stale pending ones.
  • Extended Toss Payments with a head-office merchant flow for B2B orders: idempotent confirmation, cancel and refund, fee and settlement tracking.
  • Implemented configurable payroll settlement periods and migrated legacy member data with re-runnable scripts, verified on staging first.

BitBuild · Multi-tenant construction procurement SaaS

Main Backend Engineer · Team of 4 · first sprint to production

  • Restructured the codebase into a multi-module hexagonal architecture, with ArchUnit tests enforcing boundaries.
  • Used idempotency keys against duplicate purchase orders and advisory locks for run-once scheduled jobs.
  • Set up GitLab CI and Docker Compose deployments with health checks.
  • Built multi-tenant authentication: JWT with refresh-token rotation, Redis-based revocation, social login, and RBAC with data scopes (self, assigned sites, tenant-wide).
  • Owned the domain model, PostgreSQL schema, and REST APIs for procurement, contract, approval, and supplier modules.

Miribom · Beauty booking with AI face simulation

Backend Engineer · Team of 9 · live at miribom.kr

  • Built Kakao AlimTalk notifications end to end: template APIs and an outbox-based sender with SKIP LOCKED claiming, retry with back-off, and SMS fallback.
  • Integrated the Spring backend with a FastAPI AI service: async jobs with status polling, retry limits, and locking against duplicate re-queues.
  • Owned production releases through GitLab CI on self-hosted runners, with Docker Compose builds and Caddy reverse proxy reload.
  • Delivered refund flows and card payment for deposits with Toss Payments.

Unit Technology Corporation · Backend Software Engineer, R&D

11/2024 – 03/2026

Signature Hub · Centralized digital signing platform

Backend Software Engineer · Team of 4 · banks and enterprises

  • Built backend services for signing through HSM, remote-signing providers, and VNeID.
  • Worked on the event-driven signing flow across Spring Boot microservices on Kafka.
  • Implemented PDF signing and validation (PAdES, PKCS#7) with HSM integration via PKCS#11.

ACH Gateway · NAPAS interbank payment gateway

Backend Software Engineer · Team of 12 · banking

  • Implemented inward-deposit processing on ISO 20022 pacs.008 with validation, business rules, status tracking, and process logging.
  • Developed reconciliation against NAPAS and Core Banking records to detect mismatches.
  • Optimized SQL for transaction logs and latest-status lookup.
  • Implemented the camt.033 copy-transaction flow.

Paperless · Digital signature module

Main backend of the signing module · Team of 6

  • Built internal signing, external signing by email, and third-party eSign integrations including VNeID.
  • Implemented signature revert and signer reassignment so an in-progress flow can roll back or change signers without restarting.
  • Fixed bugs and refactored the module to keep multi-step signing workflows stable.

Easy Doc · Document automation for Standard Chartered

Backend Software Engineer · Team of 5 · banking

  • Built backend APIs for digital forms and document automation on the Paperless platform.
  • Implemented document processing and multi-level approval workflows with Activiti BPMN.
  • Developed Quartz batch jobs on SQL Server and covered services with JUnit and Mockito.

JCanary Core · Internal Java and Spring framework

Backend Software Engineer · Team of 5 · in-house platform

  • Contributed reusable modules: secrets management with HashiCorp Vault, multi-database data access, storage abstraction, and shared HSM signing utilities.

Laptrinhjavaweb · Backend Developer

09/2023 – 10/2024

Java backend development.

Straffico · Freelance Backend Engineer

08/2025 – Present

Straffico · Project and cost control for construction companies

Backend Engineer · Freelance · Java 21

  • Built the GitHub Actions deployment for dev and prod: the JAR is built on the runner, then a blue-green switch releases it with zero downtime.
  • Added a deploy lock so two repositories never release to the same server at once.
  • Reconciled actual and system fund balances, and built analytics, report builder, and resource schedule APIs.
  • Added Web Push notifications, user activity audit, and support request IDs correlated across responses and logs.

Education & certification

  • Can Tho University · Software Engineering09/2021 – 05/2025
  • Linux Professional Institute (LPI) · Linux certification12/2024