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I bring over 10+ years of expertise in Java, Spring Boot and Cloud technologies. I have consistently delivered robust, scalable, and maintainable software solutions. My passion lies in tackling complex challenges head-on and transforming them into elegant, efficient optimize code. Whether you are looking to build a new application from the ground up, optimize an existing system or solve a specific problem, I bring a wealth of experience and a results driven perspective to ensure your project's success. Let's use Java to make your vision a reality, together. Key Technologies: ✅ Java 8 to 21 ✅ Spring MVC, Spring Boot, Spring Cloud Microservices, Spring Security (JWT, OAuth 2.0) ✅ Hibernate, JPA, JDBC ✅ Restful API, GraphQL ✅ Desktop application: JavaFx ✅ Spring Batch, Scheduler ✅ Frontend: JSP, Thymeleaf ✅ Relational DB: MySQL, PostgreSQL, Oracle ✅ NoSQL DB: MongoDB, Elasticsearch ✅ DB Migration: Liquibase ✅ Asynchronous Messaging: Apache Kafka, RabbitMQ ✅ Build Tool: Apache Maven, Gradle ✅ Version Controller: Git, GitHub ✅ Testing with Junit, Mockito ✅ API Documentation: Swagger UI ✅ Architecture: Monolithic, Microservice ✅ CI/CD Pipeline: Jenkins ✅ Containerization: Docker ✅ Orchestration: Kubernetes ✅ Cloud: AWS, GCP ✅ Monitoring Tools: Log4j, Slf4j, Datadog ✅ Code Quality Tools: SonarQube, Black Duck, Harbor, SecHub Scan ✅ Performance Testing Tool: JMeter ✅ Server: Apache Tomcat ✅ Realtime Scheduler: Quartz ✅ API Integration (Office365, Twilio) ✅ Libraries: Apache POI ✅ Agile Methodologies: Jira, Confluence, Scrum, Sprint Planning, Standup, Retrospectives ✅ Business & Technical Analysis: Requirements Gathering, Risk Analysis, Technical Design, Application Modeling, Implementation Planning and Support Favorite Topics: ⭐ Problem Solving Ability. ⭐ Provide Efficient Optimized Solutions. ⭐ Maintaining Good Quality Code. ⭐ Accepted Challenges That Allows Me to Learn New Skills. ⭐ Test Driven Development. ⭐ Always Prioritize Security Aspects. ⭐ Build automation. Domain Expertise: ✅ Manufacturing ✅ E-Commerce ✅ Education Services ✅ Applicant Tracking System (ATS) ✅ Customer Relationship Management (CRM) Let’s Connect ! 🎉 If you’re looking for a dedicated backend Java developer who can deliver results, I’d love to discuss your project further. Feel free to reach out, and let’s create something amazing together! Thank You

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.

Lead Back-End Engineer | Java + Spring | Building scalable, secure, and investor-ready products For 9+ years, I’ve been helping startups and growing businesses build reliable, fast, and maintainable back-ends that actually support scale — not just run. 💡 What you get working with me: Architecture that lasts: I design solutions that stay clean and efficient even as your product grows. Speed and clarity: Delivering results fast — with clear documentation and full transparency. Cross-domain expertise: Healthcare, E-Commerce, IoT, CRM, E-Learning. I understand business logic, not just code. AI & ML integration: GPT-based and ML-driven systems for smarter automation. Tech stack: Java, Spring (Boot, Security, Data, Batch), Hibernate, PostgreSQL, MongoDB, Redis, Elasticsearch, RabbitMQ, Docker, Jenkins, Linux, GitLab CI/CD. ✅ Bonus: I write clean, test-covered code (JUnit, Selenium) and handle deployment — from staging to production. Let’s turn your concept into a fast, stable, and scalable system. 📩 Message me to discuss your current challenge — I’ll help you find the smartest solution.

I am Full Stack Java developer with 10+ years of experience building and integrating scalable healthcare solutions for the US market. I specialize in healthcare interoperability, connecting EHR/EMR systems using HL7 and FHIR, and designing secure, compliant data exchange architectures. I have delivered multiple healthcare integration projects involving real-time and bidirectional data exchange across systems like Epic, Cerner, Meditech, and eClinicalWorks. My work includes building interfaces using Mirth Connect, developing FHIR-based APIs, normalizing clinical data (LOINC, SNOMED, ICD), and enabling seamless interoperability across hospital systems and HIE platforms. In parallel, I design and implement AI-enabled healthcare solutions that improve clinical workflows and data usability. I have hands-on experience building AI features such as automated clinical note summarization, patient-friendly discharge summaries, and intelligent extraction of structured data from unstructured EHR notes using NLP techniques. I’ve also worked on integrating lightweight AI modules into existing applications to support decision-making, reduce manual effort, and enhance provider productivity. My AI work is focused on practical, production-ready implementations, including integrating LLM-based services via APIs, building backend pipelines for clinical data processing, and ensuring outputs are compliant with healthcare data standards and privacy requirements. I bring strong experience across the full development lifecycle, from architecture to deployment, with a focus on scalability, performance, and clean system design. Core Expertise:- -Full Stack Development: Java, J2EE, Spring Boot, Microservices -Healthcare Integration: HL7 (v2.x), FHIR APIs, EHR/EMR interoperability -Integration Engines: Mirth Connect, interface development, data mapping- AI in Healthcare:- -Clinical text summarization (SOAP notes, discharge summaries) -NLP-based entity extraction (medications, allergies, labs) -Patient data normalization and structuring -LLM/API integration for healthcare use cases -Workflow automation using AI -Cloud & APIs: RESTful services, scalable and secure architectures Healthcare Domain Experience:- -Strong understanding of US healthcare workflows including Medicare, Medicaid, and claims processing -Expertise in compliance standards: HIPAA, PPACA -Clinical coding & standards: LOINC, SNOMED, ICD-9/10 -HL7 message types: ADT, ORM, ORU, MDM, DFT -EHR/EMR Integrations Hands-on experience integrating with: -Epic, Cerner, Meditech, Allscripts, eClinicalWorks (eCW) -McKesson, Siemens, Amazing Charts -Orchard, Sorian, Opus and other hospital systems Cores skills:- -HL7 Integration -FHIR API Development -EHR Integration -EMR Integration -Mirth Connect -Healthcare Interoperability -Java -Spring Boot -Microservices Architecture -REST API Development -Epic Integration -Cerner Integration -Healthcare Data Standards (LOINC, SNOMED, ICD-10) -Healthcare NLP -AI in Healthcare -LLM Integration -HIPAA Compliance -Healthcare Data Exchange -Interface Development -Real-time Data Integration Delivered solutions including real-time data streaming, FHIR-based integrations, and embedded interoperability within clinical systems and devices.

I build production systems enterprises run their business on: a corporate travel booking platform integrating Amadeus GDS with airline, hotel, and car-rental suppliers for institutional clients, and AIWI Team — a multi-tenant HRMS/project SaaS I founded. In 15 years I've shipped across travel, HRMS, eCommerce, and real estate, and I still write code every day. Where I'm genuinely strong: - Travel & GDS systems — Amadeus, Sabre, Galileo, plus non-GDS suppliers (AeroCRS, Radixx, Nightsbridge, Avis/Europcar). Booking flows, fare handling, supplier aggregation, PCI-aware payment integration. - Enterprise integrations — NetSuite, SAP, Xero/QuickBooks, payment/SMS/email gateways, SSO (OAuth 2.0, SAML, Keycloak, Okta). - SaaS architecture — multi-tenancy, RBAC, audit trails, and compliance-aware design (GDPR, POPIA, PCI-DSS). - Modernization — Java 8→21 migrations, monolith→microservices on Spring Boot/Spring Cloud, AngularJS→Angular 17+ upgrades. Core stack: Java (8–21), Spring Boot/Cloud/Security, Hibernate, Angular, React, PostgreSQL/MySQL, Kafka, Redis, Elasticsearch. DevOps: AWS (EKS, ECS, Lambda, RDS), Docker, Kubernetes, Terraform, Jenkins/GitLab CI, Prometheus/Grafana. How I work: I'll tell you honestly if something is outside my depth, give estimates I can defend, and write code your next developer can maintain. Most of my client relationships run multi-year for that reason. If your project involves travel tech, complex integrations, or scaling a Java platform, send me a message — I'll give you a straight assessment before either of us commits.

⚡ Backend systems should not become fragile over time; they must stay maintainable, scalable, and reliable as products grow. I am a Backend Engineer specializing in Java, Kotlin, and Spring Boot, focused on building production-grade systems where clean architecture, long-term maintainability, and stability are critical. I combine strong backend engineering practices with practical system design to create APIs and services that remain easy to extend, debug, and operate in real-world environments. Clients work with me when system quality, clean code, and scalable backend architecture matter, not just feature delivery. 🏆 Proven Engineering Approach ✔ Clean, maintainable backend architecture ✔ Production-focused development mindset ✔ Long-term scalability and reliability focus ✔ Clear communication and structured collaboration 🚀 Core Capabilities ☕ Backend Engineering with Java & Kotlin • Spring Boot application development • REST API design & implementation • Business logic architecture • Secure and maintainable backend systems • Performance-focused backend development 🏗 Scalable System Architecture • Microservice-based architectures • Modular and maintainable code structure • Service communication patterns • Production-ready backend design • Reliability and scalability optimization 🗄 Database & Persistence Engineering • PostgreSQL, MySQL, MongoDB • Hibernate / JPA / Spring Data JPA • Query optimization & data modeling • Relational and NoSQL database design ⚙ Development & DevOps Workflow • Docker-based environments • Git-based development workflows • Unit & integration testing • CI/CD-friendly project structures 🔍 Engineering Focus 🏢 Enterprise & Business Platforms Scalable APIs • backend services • maintainable systems 🚀 Startup Products & SaaS Platforms Fast iteration • clean architecture • long-term scalability 💡 Engineering Mindset • Architecture-first thinking • Clean and understandable code • Simplicity over over-engineering • Production reliability focus • Ownership from development to deployment • Long-term maintainability mindset 🧰 Technical Stack Java • Kotlin Spring Boot • Spring MVC • Spring Data JPA REST APIs • Microservices PostgreSQL • MySQL • MongoDB Hibernate • JPA Docker • Git ✨ Why Clients Choose Me ⭐ Clean and maintainable backend architecture ⭐ Scalable production-ready systems ⭐ Strong Java & Kotlin expertise ⭐ Clear communication & accountability ⭐ Reliable engineering mindset 🚀 Ready to Build Stable, Scalable Backend Systems? If you need a backend engineer who cares about clean architecture, maintainable systems, and production reliability, I am ready to help. Let us build backend systems that stay reliable, scalable, and easy to maintain long after launch.