Java Developer · Backend Engineer

Building robust
systems with Java.

Backend development specialist with Java, Spring Framework, REST APIs and scalable architectures. Focused on clean code, performance and long-lasting solutions.

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// overview
Experience +5 yrs
Projects delivered +12
Companies served 3
APIs built +30
// core stack
Java 17+ Spring Boot REST SOAP PostgreSQL Docker
// 01 — STACK
CORE
Java Platform
Java 8–21 Java EE Jakarta EE Maven Gradle JUnit
FRAMEWORK
Spring Ecosystem
Spring Boot Spring MVC Spring Security Spring Data JPA Spring Cloud
API
Integration & APIs
REST RESTful SOAP / WSDL Swagger OpenAPI JWT / OAuth2
DATA
Database
PostgreSQL MySQL Oracle DB Hibernate Redis MongoDB
// 02 — PROJECTS

Projects developed

Backend solutions built in personal and professional projects — solid architectures, clean code, and APIs that scale.

001 — Featured ● Live

Financial Management System

Full RESTful API for enterprise financial control. JWT authentication, real-time reports, legacy system integration via SOAP and microservices architecture with Spring Cloud.

Java 17 Spring Boot 3 Spring Security PostgreSQL SOAP Docker REST API
View project
@RestController
@RequestMapping("/api/v1")
public class FinanceCtrl {
 
  @Autowired
  private FinanceService svc;
 
  @GetMapping("/report")
  public ResponseEntity<Report>
  getReport() {
    return ResponseEntity
     .ok(svc.generate());
  }
}
002 ● Live

Legacy SOAP Integration

Integration middleware between legacy systems (SOAP/XML) and modern REST APIs. Data transformation, error handling and automatic retry.

Java 11 Spring WS SOAP JAXB Oracle DB
View details →
003 ◐ In development

Centralized Auth API

Centralized authentication and authorization service with OAuth2, OpenID Connect and JWT token management for multiple applications.

Spring Security OAuth2 JWT Redis
View details →
004 ● Live

Personal Portfolio

Full-stack portfolio with Node.js backend, multi-container Docker setup with Traefik reverse proxy, automated SSL, CI/CD via GitHub Actions and transactional email via Resend.

Node.js Docker Nginx Traefik Resend GitHub Actions
View details → + Case study
✅ Positives
  • Complete end-to-end ownership — from design to production deployment
  • CI/CD pipeline fully automated via GitHub Actions on every push
  • Multi-container architecture with clean separation of concerns
  • SSL certificate managed automatically by Traefik + Let's Encrypt
  • Transactional email with verified domain via Resend
  • Multi-language support (EN, PT-BR, FR-BE, NL-BE)
❌ Challenges
  • Traefik routing with multiple Docker networks caused hours of debugging
  • Git conflicts between local VPS edits and GitHub Actions deploy workflow
  • Resend DNS propagation required patience to verify records
  • Separating HTML/CSS/JS required Dockerfile updates not initially committed
🔧 Technical difficulties
  • Traefik v3 picks the wrong network IP when container has multiple networks — fixed with traefik.docker.network label
  • Nginx SPA fallback masked missing JS/CSS files — showed as syntax error in browser console
  • Docker build cache ignored new folders because COPY instructions were missing from Dockerfile
  • GitHub Actions git pull aborted due to local VPS changes — solved with git reset --hard
💡 Learnings
  • Always add traefik.docker.network when a container is on multiple Docker networks
  • Never edit files directly on VPS without committing — always go through Git
  • Traefik debug logs (--log.level=DEBUG) are essential to diagnose proxy issues
  • Resend is far superior to Gmail SMTP for domain-based transactional email
  • Separating HTML/CSS/JS from the start saves refactoring time later
+
Add project
// 03 — EXPERIENCE

Professional journey

Building backend solutions across different industries and contexts.

2022
—
Present

Senior Java Developer

// Company name

Microservices development with Spring Boot and Spring Cloud. REST and SOAP API design and consumption. Technical leadership in backend squad.

2020
—
2022

Mid-level Java Developer

// Company name

Maintenance and evolution of Java EE systems. Payment system integration via SOAP. Gradual migration to Spring Boot.

2018
—
2020

Junior Java Developer

// Company name

Career start with Java EE and JSF. Module development for internal ERP system. Learning design patterns and best practices.

+5 yrs
Building Java systems in production environments
+30
APIs designed and documented with Swagger / OpenAPI
3
Legacy system migrations to modern architecture
Java 8 → 21
Experience across multiple Java ecosystem versions
// 04 — CONTACT

Let's build something solid together.

Open to opportunities as a senior Java developer, freelance projects and technical consulting. If you need a robust backend, we're on the same page.

LinkedIn linkedin.com/in/gustavo-simoes
→
GitHub github.com/gustavo-as
→
Resume Download PDF
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