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As a Director of Technology, Leonardo combines deep technical expertise with strategic leadership. He excels at building resilient backends, driving architecture decisions, and aligning technology with business goals. Leonardo is a Senior Java Developer and AWS Certified Solutions Architect with 15+ years of experience designing cloud-native systems and leading cross-functional teams. He has delivered scalable, mission-critical platforms for high-growth startups and enterprises across Latin America. 🔹 Java, Spring Boot, REST APIs, Hibernate, Maven, Gradle 🔹 AWS (EC2, S3, Lambda, Route 53, CloudFront, IAM, CloudWatch, ECS, ECR, Load Balancers) 🔹 Microservices, RabbitMQ, asynchronous/event-driven architecture 🔹 MySQL, PostgreSQL, SQL optimization, Redis, Liquibase 🔹 CI/CD pipelines, Docker, Git, Bash scripting, Linux administration 🔹 Reporting & analytics: Tableau, Power BI, MyDBR, complex SQL views 🔹 Team leadership, agile delivery, digital transformation, mentoring tech teams

Senior Java Developer | Spring Boot Expert | Microservices | AWS | AI-Assisted Development I help businesses build scalable backend systems, enterprise APIs, and cloud-native applications using Java, Spring Boot, Hibernate, Microservices, AWS, PostgreSQL, MongoDB, Kafka, and modern AI-assisted development tools. With strong experience in Java backend development, I specialize in: ✔ Java 8/11/17+ Application Development ✔ Spring Boot & Microservices Architecture ✔ REST API Development & Third-Party Integrations ✔ Hibernate / JPA / Performance Optimization ✔ PostgreSQL, MySQL, MongoDB ✔ Event-Driven Systems (Kafka, Messaging) ✔ AWS, Docker, Kubernetes ✔ Secure APIs (Spring Security, JWT, OAuth) ✔ Legacy System Modernization ✔ Full-Stack Development (Angular, Node.js) ✔ AI-Assisted Development using ChatGPT, Claude AI, and GitHub Copilot What I Deliver • Production-grade Java Spring Boot applications • High-performance backend APIs • Scalable microservices architectures • Enterprise integrations and data-driven systems • Performance tuning, debugging, and system optimization • Cloud-ready deployments on AWS Why Clients Hire Me I focus on clean architecture, maintainable code, and practical solutions not overengineering. By leveraging modern AI tools like ChatGPT, Claude AI, and GitHub Copilot, I accelerate development, improve code quality, generate documentation, and speed up debugging while ensuring every solution is thoroughly reviewed and production-ready. Whether you need: • A Spring Boot developer for a SaaS platform • A Java backend developer for APIs, integrations, or cloud applications • Help with microservices, performance optimization, or legacy modernization • A developer who combines deep engineering expertise with AI-assisted productivity I can help. I've worked on complex backend systems involving real-time event processing, enterprise integrations, database-intensive workflows, cloud-native deployments, and event-driven architectures. If you're looking for a reliable Java/Spring Boot expert who takes ownership, communicates proactively, and delivers scalable solutions on time, let's discuss your project.

AI Engineer and Solutions Architect with 10+ years of experience building scalable SaaS platforms, enterprise systems, and cloud-native applications. Over the past two years, I have been helping businesses integrate Generative AI, Large Language Models (LLMs), AI Agents, Retrieval-Augmented Generation (RAG), and workflow automation into production systems. I specialize in OpenAI, Claude, GPT-4, LangChain, LlamaIndex, Vector Databases, AI Chatbots, AI Search Systems, and enterprise-grade backend architecture using Python, Java, Spring Boot, AWS, PostgreSQL, MongoDB, Docker, and Kubernetes. I help companies move beyond AI demos and build production-ready AI products that scale securely and reliably. Over the last 10+ years, I’ve architected and scaled SaaS platforms, enterprise systems, and cloud-native applications used by startups and growing businesses across healthcare, fintech, logistics, travel, AI, and real estate industries. I specialize in Java, Spring Boot, Microservices, AWS, PostgreSQL, MongoDB, Kubernetes, and scalable backend architecture for high-performance SaaS platforms. Worked on platforms handling real-time workflows, payment systems, enterprise reporting, AI integrations, booking engines, analytics systems, and multi-tenant SaaS infrastructure. I’ve developed enterprise-grade platforms for healthcare, fintech, e-commerce, and real-time applications, focusing on scalability, security, and long-term maintainability. My expertise includes: ✔ High-performance REST APIs ✔ Microservices architecture ✔ Cloud-native AWS deployments ✔ Authentication & payment systems ✔ Enterprise integrations ✔ Performance optimization Whether you need to modernize a legacy Java application, build a backend from scratch, or scale an existing SaaS platform, I can help architect and deliver reliable production-ready systems. My Core Competencies 1. Java Development: - Core Java: In-depth knowledge of Java’s features, collections, concurrency, and multi-threading - Spring Framework: Expertise in Spring Boot, Spring MVC, Spring Security - Microservices: Designing and implementing microservices architecture with Spring Cloud - API Development: RESTful APIs with JWT, OAuth, and GraphQL integration 2. Mobile App Development: - Android Development: Skilled in developing native Android apps using Java and Kotlin - App Lifecycle: From UI/UX design to API integration and deployment 3. Database & Back-End: - Database Expertise: Proficient in MySQL, PostgreSQL, and MongoDB for secure, scalable data management - ORM: Working with Hibernate for object-relational mapping - Server-Side Scripting: Building efficient backends with Java and Spring. 4. Deployment & Cloud: - Cloud Deployment: Expertise in deploying Java-based applications on AWS, Azure, and Google Cloud - Containerization: Proficient with Docker for application containerization and management 5. Security & Performance: - Application Security: Implementing secure systems with Spring Security, OAuth, and data encryption - Performance Tuning: Optimizing application speed, database queries, and server-side performance AI & Generative AI Expertise ✔ AI Chatbot Development ✔ OpenAI API Integration ✔ Claude AI Integration ✔ GPT-4 Applications ✔ AI Agents & Agentic Workflows ✔ Multi-Agent Systems ✔ Retrieval-Augmented Generation (RAG) ✔ AI Knowledge Bases ✔ Enterprise Search Systems ✔ Semantic Search ✔ Embedding Models ✔ Vector Databases ✔ Document AI ✔ AI Workflow Automation ✔ Conversational AI Platforms ✔ AI SaaS Products ✔ LLM Evaluation & Optimization ✔ Prompt Engineering ✔ AI API Development ✔ AI Automation for Business Processes Industries I Serve - E-Commerce: Custom checkout systems, payment gateway integration, and scalable shopping carts - Healthcare: HIPAA-compliant mobile apps and backend systems for patient management - Finance: Developing secure and efficient transaction systems, real-time data processing - Education: Learning platforms and mobile apps to enhance educational experiences - Travel & Hospitality: Building booking engines, itinerary planners, and travel apps - Real Estate: Custom property listings, user-friendly property search apps What I Can Help You Build - SaaS backends - REST APIs - Microservices architecture - Authentication systems - Payment integrations - Cloud deployment pipelines - Enterprise dashboards If you need a reliable backend engineer to build scalable APIs, SaaS platforms, or cloud-native Java applications, let’s discuss your project. Keywords: Spring Boot, Java Backend, SaaS Development, REST API, Microservices, AWS, Scalable Applications, SaaS Architecture, Platform Engineering, Distributed Systems, Event-Driven Architecture, Cloud-Native Development, Enterprise APIs, Multi-Tenant SaaS, AI Integrations, Kubernetes, Docker, Kafka, DevOps, System Design, Scalable Infrastructure, High Availability Systems, Fintech, Healthcare Platforms, Booking Engines, Real-Time Systems

🚀 I build scalable backend systems and full-stack applications for SaaS platforms, startups, and enterprises — with 5+ years shipping production Java / Spring Boot systems, and hands-on MERN stack experience when projects call for a JavaScript-based full-stack build. I currently work as a Senior Software Engineer on Xcelerate, a microservices-based SaaS platform for restoration companies, where I develop and maintain 20+ Spring Boot microservices, build real-time messaging systems, and integrate third-party platforms like QuickBooks, RingCentral, Zapier, and Encircle. What I can help you build: ✔ Java & Spring Boot backend systems ✔ Microservices architecture & REST APIs ✔ MERN stack applications (MongoDB, Express, React, Node.js) ✔ Third-party integrations (QuickBooks, Stripe, Twilio, Zapier, RingCentral) ✔ Cloud deployments — AWS, Azure, GCP ✔ CI/CD pipelines (Jenkins, GitHub Actions), Docker ✔ Database design & query optimization (PostgreSQL, MySQL, MongoDB) ✔ Legacy system modernization (Java 8 → Java 21 migrations) Highlights: Led backend development across 20+ microservices for Xcelerate, a live SaaS platform for restoration companies Migrated infrastructure from VMs to Azure App Services, implementing Azure Front Door for traffic routing and load balancing Built WS Glam, a full-stack e-commerce platform from scratch — frontend, backend, admin panel, payment integration, and role-based access control Integrated Stripe subscription billing for Remojo and overhauled its backend architecture for scale Built a custom AML (Anti-Money Laundering) system from scratch, including case management tools and fraud detection workflows I think in terms of failure modes before I write code — what happens when a webhook fires twice, when an API rate-limits mid-sync, when a migration needs to run without downtime. I communicate proactively and hand off production-ready code with documentation to match. Let's talk about what you're building — I'll give you a straight technical assessment and a clear path forward.

I deliver production-ready Java backends that scale. With 100% Job Success and $10K+ earned across 22 contracts, I solve complex integration challenges, refactor legacy systems, and build APIs that handle real-world traffic. Client Testimonials: "Oleksandr is a genuine professional who was able to do a complex Java project for me." – Sweet Home 3D Client "Fast developer, always in contact, reasonable price policy. Would work with him again." – Spring Boot Projects Client What I Deliver: Spring Boot APIs – REST endpoints, authentication (Spring Security), database integration (JPA/Hibernate) Database Solutions – PostgreSQL schema design, query optimization, MongoDB aggregations Legacy Refactoring – Clean up messy code, introduce testing (JUnit/Mockito), containerize with Docker Third-Party Integrations – Payment gateways, calendar APIs, external data syncs Testing & Quality – Unit tests, integration tests, TestContainers for reliable deployments Tech Stack: Backend: Java (8/11/17/21), Spring Boot, Spring Data JPA, Spring Security, Hibernate Frontend: CSS/HTML, JavaScript/TypeScript Databases: PostgreSQL, MySQL, MongoDB APIs: REST, JSON/XML, Swagger/OpenAPI Testing: JUnit, Mockito, TestContainers DevOps: Docker, Maven, Git, GitHub Actions Principles: OOP, SOLID, TDD, GOF Design Patterns Why Hire Me: ✔ Fast turnaround – Average response time: 0-4 hours ✔ Clear communication – Tagged "Clear Communicator" by 5 clients ✔ Proven reliability – Top Rated, 100% Job Success, no failed contracts ✔ Real-world experience – From startups to clinical trial systems Have a backend challenge? Let's architect a solution together. 📩 Send me your project details, and I'll respond with a technical approach within hours.

I'm a Full-Stack Java Developer with over 8+ years of industry experience. I excel in all aspects of Java application development, from design and development to deployment. I have a proven track record of building robust and Scalable applications across diverse domains. My Expertise Full-Stack Development: Java: Core Java, multithreading, OOP, Spring, Hibernate, Struts, J2EE. Frameworks & Libraries: Spring, Hibernate, JavaFX, Apache Struts. Microservices Architecture: Spring Cloud, Netflix OSS, service discovery, load balancing, tolerance mechanisms. Web Development: JSP, Servlets, RESTful APIs, Angular, React, HTML, CSS, JavaScript. Databases: MySQL, PostgreSQL, MongoDB, Redis. Testing & Debugging: JUnit, Mockito. I also use GitHub Copilot and Claude Code to deliver the best solutions. ✔ LLM integrations (OpenAI, Claude, etc.) ✔ AI-assisted workflow automation ✔ Prompt engineering & optimization ✔ RAG based enterprise search solutions ✔ AI code acceleration using tools like Cursor ✔ Designing AI-ready Microservices architecture Java Solution Architect: Designing scalable solutions with Java, Spring, Hibernate, and microservices. DevOps: Cloud setup, infrastructure management, CI/CD. Proficient in AWS (Lambda, EC2, S3, Redshift, SageMaker, Cognito) and GCP (VMs, Google cloud storage). Domain Experience: Insurance, finance, healthcare, e-learning, e-commerce, travel, real estate, logistics, supply chain, social networking, and education. CRM and ERP systems.