Hire the Best Core Java Developers
Mississauga, Canada
๐๐ฎ๐๐ฎ ๐๐ฎ๐ฐ๐ธ๐ฒ๐ป๐ฑ ๐๐ฒ๐๐ฒ๐น๐ผ๐ฝ๐บ๐ฒ๐ป๐ ๐ฅ๏ธ, ๐ฆ๐ฝ๐ฟ๐ถ๐ป๐ด ๐๐ผ๐ผ๐ ๐ฑ, ๐ ๐ถ๐ฐ๐ฟ๐ผ๐๐ฒ๐ฟ๐๐ถ๐ฐ๐ฒ๐ ๐ ๏ธ, ๐๐ช๐ฆ โ๏ธ, ๐ฅ๐๐ฆ๐ง ๐๐ฃ๐๐ ๐ I help businesses build scalable, secure, and high performance backend systems that handle growth without slowing down. Most applications work well in the beginning. The problems start when traffic increases. APIs become slow, deployments become risky, and maintaining the code becomes expensive. That's where I come in. ๐๐ ๐ฎ ๐ฆ๐ฒ๐ป๐ถ๐ผ๐ฟ ๐๐ฎ๐๐ฎ ๐๐ฒ๐๐ฒ๐น๐ผ๐ฝ๐ฒ๐ฟ ๐๐ถ๐๐ต ๐ญ๐ฏ+ ๐๐ฒ๐ฎ๐ฟ๐ ๐ผ๐ณ ๐ฒ๐ ๐ฝ๐ฒ๐ฟ๐ถ๐ฒ๐ป๐ฐ๐ฒ, I've helped startups and enterprise companies design, build, and optimize backend systems that scale reliably in production. I am not just a Java Developer who writes code. I help businesses create backend architectures that support growth, improve performance, and reduce technical debt. ๐ฅ๐ฒ๐๐๐น๐๐ ๐'๐๐ฒ ๐๐ฒ๐น๐ถ๐๐ฒ๐ฟ๐ฒ๐ฑ โข Built scalable Java Developer solutions serving thousands of daily users with high availability. โข Designed Microservices architectures that reduced deployment risks and improved system reliability. โข Developed Spring Boot applications that improved API response times and backend performance. โข Helped businesses migrate legacy systems into modern Java Developer architectures. โข Delivered production ready backend platforms for startups and enterprise organizations. Every project starts with a business goal and ends with measurable results. ๐ช๐ต๐ฎ๐ ๐ ๐๐ผ ๐๐ฎ๐๐ฎ ๐๐ฒ๐๐ฒ๐น๐ผ๐ฝ๐บ๐ฒ๐ป๐ โข Custom backend application development โข Enterprise Java solutions โข Legacy application modernization โข Backend performance optimization โข Secure and maintainable architecture ๐ฆ๐ฝ๐ฟ๐ถ๐ป๐ด ๐๐ผ๐ผ๐ ๐๐ฒ๐๐ฒ๐น๐ผ๐ฝ๐บ๐ฒ๐ป๐ โข REST API development โข Spring Security โข Spring Data JPA โข Authentication and authorization โข Scalable backend services ๐ ๐ถ๐ฐ๐ฟ๐ผ๐๐ฒ๐ฟ๐๐ถ๐ฐ๐ฒ๐ ๐๐ฟ๐ฐ๐ต๐ถ๐๐ฒ๐ฐ๐๐๐ฟ๐ฒ โข Distributed systems design โข Service decomposition โข API Gateway implementation โข Event driven architecture โข System scalability and resilience ๐๐ช๐ฆ ๐๐น๐ผ๐๐ฑ ๐ฆ๐ผ๐น๐๐๐ถ๐ผ๐ป๐ โข AWS deployment and infrastructure โข EC2, ECS, Lambda โข Cloud architecture design โข Monitoring and optimization โข Cost effective cloud operations ๐ฅ๐๐ฆ๐ง ๐๐ฃ๐ ๐๐ฒ๐๐ฒ๐น๐ผ๐ฝ๐บ๐ฒ๐ป๐ โข API design and implementation โข Third party integrations โข Payment gateway integration โข Documentation and testing โข Secure API architecture ๐ช๐ต๐ฎ๐ ๐ ๐ฎ๐ธ๐ฒ๐ ๐ ๐ฒ ๐๐ถ๐ณ๐ณ๐ฒ๐ฟ๐ฒ๐ป๐ Most Java Developers focus only on writing code. I focus on the business impact of the software. ๐๐ฒ๐ณ๐ผ๐ฟ๐ฒ ๐ฏ๐๐ถ๐น๐ฑ๐ถ๐ป๐ด ๐ฎ๐ป๐๐๐ต๐ถ๐ป๐ด, ๐ ๐ฎ๐๐ธ: โข Will this architecture still work when traffic grows? โข Can future developers maintain it easily? โข Is it secure? โข Is it optimized for performance? โข Can it scale without major rewrites? This approach helps clients avoid costly problems later. ๐ช๐ต๐ผ ๐ ๐ช๐ผ๐ฟ๐ธ ๐๐ฒ๐๐ ๐ช๐ถ๐๐ต โข Startups building new SaaS products โข Businesses scaling existing applications โข Companies modernizing legacy Java systems โข Teams adopting Microservices architecture โข Organizations migrating workloads to AWS โข Businesses needing secure and scalable REST APIs ๐ง๐ฒ๐ฐ๐ต๐ป๐ผ๐น๐ผ๐ด๐ถ๐ฒ๐ Java, Spring Boot, Spring Security, Hibernate, JPA, Microservices, AWS, Docker, Kubernetes, REST APIs, Kafka, RabbitMQ, PostgreSQL, MySQL, MongoDB, Redis, Maven, Gradle, Git, CI/CD, Jenkins ๐ช๐ต๐ ๐๐น๐ถ๐ฒ๐ป๐๐ ๐๐ถ๐ฟ๐ฒ ๐ ๐ฒ โข 13+ years of Java Developer experience โข Clean, maintainable code โข Scalable backend architecture โข Strong communication โข Reliable delivery โข Long term technical thinking If you're looking for a Java Developer who understands both software engineering and business objectives, let's discuss your project. Send an invitation and I'll respond within a few hours. Keywords: Java Developer, Senior Java Developer, Java Backend Developer, Java Software Engineer, Spring Boot Developer, Spring Boot Expert, Java Application Development, Enterprise Java Developer, Java Web Services, REST API Developer, RESTful API Development, Backend Developer, Backend Engineer, Microservices Developer, Microservices Architecture, Distributed Systems, AWS Developer, AWS Cloud Engineer, Java AWS Developer, Docker, Kubernetes, Kafka, RabbitMQ, Hibernate, JPA, Spring Security, API Integration, Database Design, PostgreSQL, MySQL, MongoDB, Redis, SaaS Backend Development, Scalable Application Development, Cloud Native Applications, Java Consultant, Software Architecture, System Design, Enterprise Application Development, Performance Optimization, CI/CD, Jenkins, Maven, Gradle, Full Stack Java Developer.
- Core Java
- Java
- Spring Boot
- Java Servlet API
- Java Collections Framework
- JUnit
- API
- Microservice
- Java Persistence API
- Spring MVC
- Spring Cloud
- Spring Batch
- jQuery
- jMock
- Git
Mumbai, India
Hello! I'm Swastik Srivastava, a Full Stack Developer and Big Data Consultant with over 5 years of experience delivering scalable, high-performance solutions for startups, enterprises, and global clients. I specialize in building robust systems across the Java ecosystem, Big Data architectures, and data-driven marketing platforms. My work spans across multiple domains including Scala + Spark development, data analytics, digital marketing tech stacks, and end-to-end web applications. ๐ง Core Skills & Expertise: Backend: Java (Spring Boot), Scala, Kafka, REST APIs Big Data: Spark, Hadoop, Hive, Flink, Sqoop, Airflow Cloud: AWS (S3, Lambda, Glue), GCP, Azure (Data Factory, Synapse) Frontend: JavaScript, React, HTML/CSS Databases: MySQL, MongoDB, PostgreSQL DevOps: Docker, GitHub Actions, Jenkins, CI/CD Pipelines Digital Marketing Tech: Google Analytics, Meta Ads Reporting, Marketing Funnels, Email Automation Data Analytics: ETL Pipelines, Dashboards, SQL, Python (Pandas), Power BI โ Why Work With Me? Proven track record with top-tier clients (e.g., Morgan Stanley via EY) Ability to lead full-stack projects while coordinating with cross-functional teams Clear communicator who ensures on-time, high-quality delivery You work directly with me โ I handle communication and project management, while my internal team supports execution for faster turnaround and flexibility ๐ Services Offered: โ Java + Spring Boot Microservices Development โ Big Data Pipeline Design with Spark, Scala, Kafka โ Digital Marketing Data Analysis & Automation โ Web Development & Full-Stack Application Builds โ Data Analytics Dashboards & Reporting When I'm not coding, I mentor junior developers and love solving challenging backend and data problems. I'm passionate about helping businesses unlock the full value of their data and digital infrastructure. ๐ฉ Letโs connect! Whether you need a quick fix or a long-term technology partner, Iโm always open to a conversation to understand how I can help.
- Core Java
- Android App Development
- Web Design
- API Integration
- Web Development
- Front-End Development
- Web Application
- Big Data
- Data Analysis Consultation
- Spring MVC
- Digital Marketing
- iOS Development
- PySpark
- .NET Framework
- AI Bot
Ahmedabad, India
Over the last 14 years, I have almost completed 42 android projects for different businesses and personal use of my clients. Great experience in Java, Kotlin , Jetpack Compose, Dagger HILT and other architectural component, View Based Systems, Android SDK, Google's Android related service and Android Studio. I always welcome new ideas and love to convert them in smart android application. During different applications development period I have gone through many different challenges and finish all of them with my smart work. I have been work in all below area and also willing to explore more with new things. Material Design with backward compatibility, Jetpack Compose, Navigation Component, Dagger HILT, Paging 2 and Paging 3, SQL/SQLite databases, JSON Bese data parsing, RestFull Web service integration, Room, Audio/Video Streaming, ExoPlayer, Face Recognition and OCR, Social Network - Facebook, Twitter integration, Google Map and other Google services, Other open source library integration and modification according to requirement. I am familiar with MVVM,MVC and Clean architecture pattern. I have developed some of my apps with MVVM + CLEAN architecture, including all layers, such as Presentation, Data and Domain. I have hands on experience in Kotlin Flow, LiveData and Coroutine. I am cost effective but quality work provider.
- Core Java
- In-App Purchases
- User Authentication
- Android App Development
- Application Security
- API Integration
- Mobile App Development
- Kotlin
- QR & Barcode Scanner
- Firebase
- SQLite
- Android Room Persistence
- Face Detection
- JetPack
Chernivtsi, Ukraine
I am a Senior Fullstack Developer with over 15 years of hands-on experience in building and scaling Java , C# / Net , Angular applications for startups, enterprises, and SaaS platforms. Currently, Iโm working as the Chief Technology Officer at InventorSoft, a software development agency specializing in web and mobile solutions. I bring a strategic mix of technical depth, team leadership, and product vision to every project. Why hire me๐ง: ๐ Expert in Scalable Java and .Net Architectures - Over 15 years of experience in developing Java, .Net, C#, Angular scalable applications from different domains. - Backend systems built with Spring Boot (15+ years) โ Delivered scalable microservices and high-performance business logic for enterprise-grade applications. - ORM & data access with Hibernate โ Applied advanced ORM techniques for efficient database interactions, query optimization, and data integrity in distributed systems. - Frontend development with Angular & Thymeleaf Designed and delivered 200+ robust backend systems for SaaS products, e-commerce platforms, and enterprise clients. ๐ Cloud-Native Platform Engineering Specializes in building secure, scalable, cloud-native platforms using leading cloud providers: - 8+ years of production experience with AWS โ Deployed scalable, secure, and high-availability applications. - 9+ years of hands-on Azure expertise โ Delivered enterprise-grade solutions with Azure App Services, Azure DevOps, and SQL/Azure Storage. - 5+ years of experience on Google Cloud Platform (GCP) โ Built and deployed containerized microservices using GKE, Cloud Run, and Firebase. ๐ API-First & Cloud-Native System Design - Strong background in API integration and microservice architecture. - Created high-performance APIs for platforms serving 50K+ users, ensuring seamless third-party integration and scalability. - Experienced in Docker & Kubernetes, enabling CI/CD pipelines and resilient containerized systems. ๐ Full-Stack Leadership & Agile Team Management - Led and mentored teams of 5โ25 developers through all stages of the SDLCโrequirements gathering to deployment and maintenance. - Specialized in building cross-functional teams for backend-heavy systems, modern UIs (React, Angular, Thymeleaf), and DevOps automation. My latest achievement as a Software Architect: ๐ค Partnered with 45+ SaaS companies to design and deliver secure, scalable platforms using Spring Boot, AWS, and modern cloud services. ๐ Helped 10 tech startups scale from MVP to productionโselecting the right tech stack, defining cloud-native architecture, and assembling strong dev teams. ๐ผ Enabled 5 client acquisitions through the development of enterprise-grade software that attracted major buyers and investors. ๐ญ Led a digital transformation project for a multi-billion-dollar oil company, delivering a secure, API-first platform that automated mission-critical operations. ๐งฉ Technologies I Specialize In - Languages/Frameworks: Java, C#, .Net, Spring Boot, Hibernate, Thymeleaf, .Net Core - Cloud Platforms: AWS (8+ years), Azure (9+ years), Google Cloud (5+ years) - DevOps Tools: Docker (7+ years), Kubernetes (5+ years) - Integration & Architecture: RESTful API integration, microservices, clean architecture, CI/CD pipelines Clients that I am proud of: ๐ป Shoeby โ A fashion retail platform focused on modernizing the e-commerce experience with intuitive UI, product personalization, and seamless shopping journeys. ๐ป CellRebel โ Provides advanced mobile network analytics, helping telecom companies improve coverage and performance based on real user data. ๐ป Blade โ A technology-powered aviation company offering urban air mobility services, including helicopter and seaplane flights. ๐ป Matics โ A real-time operational intelligence system for manufacturers, offering production insights and process optimization across the factory. ๐ป MedischeScholing โ A medical e-learning platform that enables healthcare professionals to access, register for, and track accredited training and certifications. โก๏ธ Learn more about other projects on the InventorSoft portfolio Keywords: Java, Backend, Developer, Fullstack, Web, Cross-Platform, Mobile, Application, AI, OpenAI, Service, App, Development, Engineer, Integration, Build, Website, Expert, Spring boot, MySQL, Development Team, Integrated, SaaS Platform, remote, Full-stack, Senior, Software, Client Management, GraphQL, API, .NET, Asp.net, Programmer, Technical Lead, Dashboard, MVC, Developers, ASP.NET, AspNetZero, core, software, MAUI, C#, Angular, .Net, Core, Principal, Performance, Scalability, Microsoft, Blazor, SQL, Server, Frontend, React, Ruby on Rails, RoR/React, front-end, Tailwind, feature, JavaScript, ROR, TailwindCSS, Technical Staff
- Core Java
- Java
- JavaScript
- API
- RESTful API
- Spring Boot
- Spring Framework
- MySQL
- HTML
- CSS
- Amazon Web Services
- Full-Stack Development
- Database
- Back-End Development
- Hibernate
Pune, India
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. โ LLM integrations (OpenAI, Claude, etc.) โ AI-assisted workflow automation โ Prompt engineering & optimization โ RAG based enterprise search solutions โ AI code acceleration using tools like Cursor โ 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.
- Java
- Spring Boot
- Spring Batch
- Python
- TypeScript
- Microservice
- MySQL
- PostgreSQL
- API
- Google Analytics
- ETL
- Angular
- Data Engineering
- Angular 5
- React
Kharkiv, Ukraine
๐ 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 ๐ช Full Stack Java Developer Expertise โ๏ธ 20+ years of Java development 100 successful projects using Java, Spring Boot, Spring Security, Hibernate, and enterprise architectures โ๏ธ Full Stack Development covering backend architecture database design frontend implementation and React Native mobile applications โ๏ธ Spring Boot Development, REST API microservices cloud-native applications and high-performance backend systems โ๏ธ Backend Architecture, distributed systems, 50 third-party integrations, authentication systems, and secure API development โ๏ธ PostgreSQL MySQL Redis AWS Docker Kubernetes CI/CD performance optimization and legacy system modernization โ๏ธ Extensive experience designing business-critical applications where scalability, maintainability, security, and long-term growth are key requirements โ๏ธ Experience integrating payment gateways, healthcare systems, cloud services, identity providers, and external enterprise platforms โ๏ธ Strong understanding of software architecture, design patterns, clean code principles, and modern development practices โ๏ธ Experience leading technical initiatives, collaborating with distributed teams, participating in code reviews, and helping businesses make technology decisions ๐ฅ 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 โ๏ธ EHR / EMR systems, telemedicine platforms, patient portals, and patient engagement applications โ๏ธ FHIR & HL7 integrations for healthcare interoperability and secure data exchange โ๏ธ React Native healthcare applications with Apple HealthKit Google Fit BLE integrations and real-time health monitoring โ๏ธ Improved patient engagement by up to 100% โ๏ธ HIPAA compliant architectures with encrypted storage, audit logging, role-based access control, and secure API โ๏ธ Java Spring Boot backend systems with up to 99.9% uptime โ๏ธ Healthcare workflow automation, provider portals, appointment management systems, and patient communication platforms. ๐ณ 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. โ๏ธ Stripe Apple Pay Google Pay and 3D Secure ( 3DS ) integrations โ๏ธ KYC & AML workflows for onboarding and compliance automation. โ๏ธ Reduced payment default rates in more than 100+ projects โ๏ธ Payment processing platforms, transaction management systems, and financial API โ๏ธ Secure fintech architectures with encrypted storage, tokenization, audit logging, and secure authentication. โ๏ธ Financial reporting systems, payment workflows, transaction monitoring, and compliance-focused software solutions. ๐ Key Results โ๏ธ 15+ years of commercial software development experience. (role Full Stack Java Developer ) โ๏ธ Built enterprise healthcare fintech and SaaS applications for startups and growing businesses โ๏ธ Achieved up to 100% uptime for mission-critical systems. โ๏ธ Improved patient engagement by up to 40% โ๏ธ Reduced payment decline rates by up to 25% โ๏ธ Improved application performance by up to 35% โ๏ธ Reduced infrastructure costs by up to 25% โ๏ธ Reduced security vulnerabilities by up to 90% โ๏ธ Modernized legacy applications through microservices adoption and cloud migration initiatives ๐ Core Technologies Java Developer โข Spring Boot โข Spring Security โข Hibernate โข React Native โข TypeScript โข PostgreSQL โข MySQL โข Redis โข Kafka โข AWS โข Docker โข Kubernetes โข REST API โข Microservices โข FHIR โข HL7 โข HIPAA โข PCI DSS โข Stripe โข KYC โข AML ๐ฉ 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.
- Core Java
- Java
- MongoDB
- Spring Framework
- SQL
- Spring Security
- React
- Spring Boot
- Back-End Development
- Front-End Development
- Full-Stack Development
- React Native
- API Integration
- Expo.io
- Angular
- TypeScript
- Apache Kafka
- Microservice
- Web Development
- JavaScript
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At A Glance: Core Java
Developing and programming software is the backbone of many modern businesses and industries. Programs and applications can be created to fill many different roles, including games, e-commerce, and interactive web content. These applications can be used internally for tracking and managing other digital resources, or developed as standalone software to distribute to customers and consumers. One important feature of any program is that it is written and developed in a programming language that allows it to be easily ported and executed on other computer systems. Core Java, commonly known as Java Standard Edition (SE), is one such programming language that gives you the portability and flexibility in your developed software that you need for your business and project. Taking advantage of an experienced Java developer or programmer is the most effective way to leverage this powerful language.
Java developers and programmers available on Upwork generally possess a deep knowledge and skill set. Backgrounds include building, writing, and developing programs from the ground up for a wide variety of uses. Java developers and programmers also have experience working with existing applications by adding additional functions or features. Core Java developers and programmers are highly computer-literate professionals with advanced mathematical skills and frequent experience working with other computer programming languages and development frameworks. The portable nature of applications written in Core Java lead to programmersโ and developersโ comfort with many different systems, which fills dynamic roles within a business or project.
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