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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.

⭐⭐⭐⭐⭐ Top Rated Plus on Upwork 100% Job Success Score I'm a Java developer with 8+ years delivering production-grade systems from serverless AWS architectures to distributed microservices serving healthcare and fintech clients. 𝗪𝗵𝗮𝘁 𝗜'𝘃𝗲 𝗕𝘂𝗶𝗹𝘁 ➡ As lead Java developer at my current company, managed a team of 8 engineers over 7 years — delivering 4 production systems across healthcare, fintech, and AI verticals. ➡ Designed serverless AWS infrastructure for a US longevity and healthcare platform as an AWS developer — Lambda, AppSync, DynamoDB, Cognito, SNS/SQS, Stripe, HubSpot currently in production. ➡ Led migration from monolithic Spring apps to distributed microservices — reducing deployment complexity and enabling independent scaling per service. ➡ Built a PDF/UA accessibility compliance platform as backend developer using Java 21, iText 7, PDFBox, veraPDF processing and remediating documents of hundreds of pages against international accessibility standards. ➡ Delivered an AI-powered workflow automation platform as an AI developer integrating Spring AI, Azure cloud, and automated Stripe subscription workflows. ➡ Shipped a medical practitioner dashboard integrating 3rd-party hardware APIs and clinical toolkits as backend developer and tech lead serving real patients and practitioners in production. Core experience as a Java developer and Backend developer As a Java developer with 8+ years in production systems, my core is Java 8 through Java 21 with the full Spring ecosystem Boot, Cloud, Security, WebFlux, Batch, and Spring AI for AI-integrated backends. I work across both relational (PostgreSQL, MySQL) and NoSQL (MongoDB, DynamoDB, Redis) databases, selecting the right store based on access patterns not habit. As a backend developer I've optimised slow MongoDB queries to cut response times, redesigned DynamoDB access patterns for a high-throughput healthcare API, and built Redis caching layers that kept latency flat under load. As an AWS developer, my hands-on stack covers Lambda, AppSync, DynamoDB, Cognito, SQS, SNS, SES, S3, API Gateway, Route 53, and CloudFormation built and maintained in a live US healthcare platform. I design serverless pipelines end-to-end, not just deploy to them. For async workloads I wire event-driven systems using Kafka, RabbitMQ, or AWS SNS/SQS depending on durability and throughput requirements. On the container side: Docker, Kubernetes, Helm, OpenShift, Terraform, and Jenkins full IaC from infrastructure definition to CI/CD pipeline. As an AI developer, I've shipped Spring AI integrations for workflow automation backends, built document intelligence services capable of processing and remediating hundreds-of-pages PDFs against accessibility standards, and connected GraphQL APIs via AWS AppSync for mobile and web AI-driven applications. I also have production experience integrating medical hardware APIs, Stripe subscription billing, and HubSpot CRM sync into Java backends the kind of third-party integration work every backend developer eventually owns in a real product. AWS Developer & 𝗖𝗹𝗼𝘂𝗱 𝗘𝗻𝗴𝗶𝗻𝗲𝗲𝗿𝗶𝗻𝗴 ✅ Currently operating as AWS developer on a live healthcare platform Lambda, AppSync, DynamoDB, Cognito, SQS/SNS/SES, S3, API Gateway, Route 53, CloudFormation ✅ Experience as AWS developer across serverless, containerized (ECS/K8s), and IaC (Terraform, CloudFormation) environments ✅ Also experienced across Azure (AKS, Azure DevOps) and GCP as multi-cloud backend developer ✅ Kubernetes, Helm, Docker, OpenShift, Jenkins, Terraform the full DevOps chain every AWS developer deploys through AI developer 𝗖𝗮𝗽𝗮𝗯𝗶𝗹𝗶𝘁𝗶𝗲𝘀 ✅ Delivered AI-powered backend services as AI developer using Spring AI automated content generation and workflow orchestration at scale ✅ AWS AppSync + DynamoDB + Cognito pipeline for a live healthcare platform: the architecture an AI developer builds when latency and data integrity are non-negotiable ✅ Experienced AI developer integrating third-party AI tooling with enterprise Java backends designing event-driven pipelines that handle async AI workloads via Kafka and SQS ✅ As AI developer, built document intelligence features automated PDF tagging, structure remediation, and accessibility validation across large document corpora 𝗜𝗻𝗱𝘂𝘀𝘁𝗿𝗶𝗲𝘀 Healthcare · Fintech · SaaS · E-commerce · Logistics · Telecom · IoT · Blockchain · Automotive · Media 𝗦𝗽𝗲𝗰𝗶𝗮𝗹𝗶𝘇𝗮𝘁𝗶𝗼𝗻𝘀 & 𝗥𝗼𝗹𝗲𝘀 ✔ Senior Java Developer · Java Spring Boot Developer · Java Backend Developer ✔ AWS Cloud Engineer · AWS DevOps Engineer ✔ Azure Cloud Engineer · Google Cloud Engineer ✔ AI Backend Developer · Full-Stack Developer (Spring Boot + React) ✔ AI Backend Developer · Full-Stack Developer (Spring Boot + React) Need a Java developer, backend developer, AWS developer, or AI developer who ships production systems — not prototypes? Drop me a message. 04/06/2026

Hello, my name is Dimytro. I am Java developer from Kyiv, Ukraine. I am developing Java since 2019.

📢 Available for New Projects 📢 I am a Senior Java Developer and Full Stack Developer with 10+ years of experience building production-grade backend systems, SaaS platforms, and web applications that scale globally. As a Java Developer and Full Stack Developer, I specialize in transforming complex business requirements into reliable, high-performance software solutions. Why hire me as your Java Developer and Full Stack Developer? ⭐ 100% Job Success Score ☕ 10+ years of commercial Java development across enterprise and startup environments 🚀 30+ production systems — SaaS platforms, web apps, APIs, and microservices ⚙️ Expert Java Developer in Spring Boot, Spring Cloud, Hibernate, and microservices 💰 Built fintech Java backend processing $15M+ annually on AWS 📈 Scaled logistics platform to 1.2M+ daily API requests with Redis optimization 🏆 Delivered Full Stack Developer MVP in 6 weeks securing $500K+ pre-seed funding 🖥️ Full Stack Developer — Java backend + React + Node.js + REST API ☁️ AWS, Docker, Kubernetes, CI/CD pipelines 🗄️ PostgreSQL, MySQL, MongoDB ✅ TDD, SOLID principles, clean architecture, Agile 👥 Led 10+ developer teams across full-cycle SaaS delivery What I build as a Java Developer and Full Stack Developer: As a Java Developer, I design backend systems, REST APIs, and microservices that power SaaS platforms, web applications, and enterprise software. As a Full Stack Developer, I cover the complete stack — Java Spring Boot backend, PostgreSQL database, React frontend, and AWS cloud deployment. I have delivered SaaS platforms, CRM systems, ERP solutions, marketplace platforms, booking systems, fintech applications, healthcare platforms, logistics systems, and EdTech products. Industries served: 🏦 Fintech — payment processing, financial SaaS, embedded financing 🏥 Healthcare — HIPAA-compliant platforms, patient management systems 🚚 Logistics — real-time tracking, fleet management, delivery platforms 🛒 E-commerce — marketplace platforms, inventory and order systems 📚 EdTech — learning management systems, educational SaaS platforms 🏗️ Construction — project management, field operations, procurement 📊 SaaS — multi-tenant architecture, subscription billing, dashboards Technical expertise: Backend: Java, Spring Boot, Spring Cloud, Spring Security, Hibernate, Microservices, REST API, Kafka, Redis, OAuth2, JWT Full Stack: React, Next.js, TypeScript, Node.js, NestJS, Redux, Tailwind CSS Cloud: AWS (EC2, S3, RDS, Lambda), Docker, Kubernetes, Jenkins, GitHub Actions, Terraform Databases: PostgreSQL, MySQL, MongoDB, Redis, Elasticsearch Integrations: Stripe, Plaid, Firebase, Twilio, QuickBooks, OpenAI API, Claude API What I deliver: ✅ SaaS platform development from MVP to production ✅ Web application development and modernization ✅ REST API design and microservices architecture ✅ Third-party API integrations ✅ Fintech and payment system development ✅ Marketplace and booking platform development ✅ Custom CRM, ERP, and internal tooling ✅ Cloud infrastructure setup and optimization As a Java Developer and Full Stack Developer, I think about architecture, scalability, and maintainability from day one. Whether you need a Java Developer for a critical backend service, a Full Stack Developer to build your SaaS platform, or a technical partner to architect your web application — I deliver production-ready results. Looking for a Java Developer, Full Stack Developer, Spring Boot Developer, SaaS Developer, or Web Application Developer who builds systems that scale? Let's talk 🚀

I'm a Java developer and full stack developer with 5+ years building backend systems, REST APIs, microservices, and full stack web applications. As a full stack developer, I work end-to-end with Java and Spring Boot on the backend, React and Angular on the frontend, but backend engineering is where I spend most of my time and add the most value. On the backend, my core stack is Java, Spring Boot, and Spring Framework, with REST APIs, Hibernate/JPA, PostgreSQL, MySQL, MongoDB, and SQL for persistence. As a backend developer, I've designed 120+ REST APIs and built 10+ microservice architectures from the ground up, for systems serving anywhere from 10K to 500K+ users depending on project scale. I've shipped 35+ production projects as a full stack developer and Java developer, across fintech, logistics, telecommunications, retail, SaaS, healthcare, and enterprise. For infrastructure, I work across AWS, GCP, and Azure, and I'm comfortable with Docker, Kubernetes, and CI/CD pipelines to keep backend systems reliable in production as part of full stack delivery. Performance is something I take seriously as a backend developer: on several engagements, I've cut API response times by up to 60% and improved overall system performance by 40%+ through targeted refactoring and architectural improvements, rather than costly rewrites. I've also worked extensively with enterprise-level database schemas, writing and optimising complex SQL queries, indexing strategies, and data models across tables with 100K+ records. The production systems I've maintained as a Java backend developer have consistently held 99.9% uptime, that doesn't happen by accident. It comes from solid monitoring, thoughtful deployment practices, and knowing where the failure points are before they become incidents. When a project calls for it, I also write Python, PHP, and Node.js, and handle frontend work in React or Angular including JavaScript for client-side logic, but as a full stack developer, my strongest work is where backend architecture meets a clean frontend implementation My clients get clear communication, fast responses, and code that's actually maintainable six months later. I'm business-focused and I care whether the thing solves your problem, not just whether it compiles. As one client put it: he doesn't just write code, he thinks about why we need it in the first place. Beyond hands-on Java development, I've led teams, mentored junior developers, and run cross-functional projects where the technical and human sides both needed managing. I'm open to long-term collaborations and challenging projects involving Java, Spring Boot, full stack development, backend architecture, React, Angular, cloud systems, and microservices. Need a full stack developer, Java developer, or backend developer who ships clean code and tells you when you're building the wrong thing? That's the conversation worth having. Drop me a message.

👋 I'm a Senior Full Stack Java Developer with 20+ years of experience building enterprise software, healthcare platforms, fintech solutions, SaaS products, and mobile applications. As a Java Developer I've built high-load backend systems, REST AP payment solutions document processing platforms, and business applications used by thousands of users. As a Full Stack Developer and React Native Developer I've helped startups and growing companies launch scalable products while maintaining security, performance, and compliance. Throughout my career, I've worked with startups, established businesses, and enterprise clients, helping them transform ideas into reliable software products. My experience covers the entire development lifecycle, from architecture planning and technical discovery to development, deployment, optimization, and long-term support. My expertise includes Java Developer Spring Boot React Native AWS PostgreSQL Docker Kubernetes microservices cloud infrastructure and secure software architecture 💪 Full Stack Java Developer Expertise ✔️ 20+ years of Java development 100 successful projects using Java, Spring Boot, Spring Security, Hibernate, and enterprise architectures ✔️ Full Stack Development covering backend architecture database design frontend implementation and React Native mobile applications ✔️ Spring Boot Development, REST API microservices cloud-native applications and high-performance backend systems ✔️ Backend Architecture, distributed systems, 50 third-party integrations, authentication systems, and secure API development ✔️ PostgreSQL MySQL Redis AWS Docker Kubernetes CI/CD performance optimization and legacy system modernization ✔️ Extensive experience designing business-critical applications where scalability, maintainability, security, and long-term growth are key requirements ✔️ Experience integrating payment gateways, healthcare systems, cloud services, identity providers, and external enterprise platforms ✔️ Strong understanding of software architecture, design patterns, clean code principles, and modern development practices ✔️ Experience leading technical initiatives, collaborating with distributed teams, participating in code reviews, and helping businesses make technology decisions 🏥 Healthcare Software Development Expertise As a Senior Java Developer and Full Stack Developer, I've built secure and HIPAA-compliant healthcare software for startups, clinics, and digital health companies. ✔️ 100+ healthcare applications including EHR/EMR systems, telemedicine platforms, patient portals, and engagement solutions ✔️ 80+ FHIR & HL7 integrations for healthcare interoperability and secure data exchange ✔️ 150 React Native healthcare apps with Apple HealthKit, Google Fit, BLE, and real-time health monitoring ✔️ 100+ healthcare features delivered, improving patient engagement and clinical workflows ✔️ 50+ HIPAA-compliant architectures with encrypted storage, audit logging, RBAC, and secure APIs ✔️ 100 Java Spring Boot backend systems with up to 99.9% uptime ✔️150+ healthcare workflow automations, provider portals, appointment management, and patient communication platforms 💳 Fintech Software Development Expertise As a Full Stack Java Developer I've built PCI DSS-compliant fintech platforms focused on payments, identity verification, and transaction security. ✔️ 30+ Stripe, Apple Pay, Google Pay, and 3D Secure (3DS) integrations ✔️ 20+ KYC & AML workflows for onboarding and compliance automation ✔️ 100+ payment features delivered, reducing friction and improving transaction success ✔️ 25+ payment platforms, transaction systems, and financial API integrations ✔️ 15+ PCI DSS architectures with encryption, tokenization, audit logging, and secure authentication ✔️ 50+ financial reporting, payment workflows, transaction monitoring, and compliance solution 🏆 Key Results ✔️ 20+ years of commercial experience as a Full Stack Java Developer ✔️ 100+ enterprise projects across Healthcare, FinTech, SaaS, and AI ✔️ 55+ AI-powered products using OpenAI, Claude API, FastAPI, AI Agents & RAG ✔️ Up to 100% uptime for mission-critical healthcare and fintech systems ✔️ Up to 40% higher patient engagement through digital health solutions ✔️ Up to 25% lower payment decline rates with optimized payment workflows ✔️ Up to 35% faster application performance and scalability improvements ✔️ Up to 90% fewer security vulnerabilities with secure architectures 📌 Core Technologies Java Developer • Spring Boot • Spring Security • React Native • TypeScript • PostgreSQL • MySQL • Redis • Kafka • AWS • Docker • Kubernetes • REST API • Microservices • HIPAA • Stripe 📩 Looking for a technical partner who understands both technology and business goals? I help companies build, scale, and modernize Healthcare Fintech SaaS and Enterprise products using Java Spring Boot Full Stack technologies and React Native If you're looking for more than just code, let's discuss your project and how I can help.