Senior Java Developer – Spring Boot, Microservices & Multithreading (W2 ONLY)

**** W2 ONLY - NO C2C - NO VISA SPONSORSHIP AVAILABLE **** Senior Java Developer - Spring Boot, Microservices & Multithreading (W2 ONLY) Location: Englewood Cliffs, NJ Duration: Long-Term, Ongoing Contract Experience: 8+ Years Position Type: Contract Work Arrangement: Hybrid - 3 days a week onsite About the Opportunity We are seeking a highly skilled Senior Java Developer to join the engineering team of a leading media and technology organization. The ideal candidate will have deep expertise in Core Java, Spring Boot, microservices architecture, multithreading, and high-performance backend application development. This role involves designing, developing, and optimizing scalable, reliable, and high-throughput backend services supporting complex, data-intensive enterprise applications. We are looking for a technically strong, hands-on engineer who understands Java internals, concurrent programming, distributed systems, and production-level performance optimization. Key Responsibilities Design, develop, and maintain high-performance backend applications using Java and Spring Boot. Build scalable, resilient microservices and RESTful APIs. Develop and optimize multithreaded and concurrent Java applications. Implement efficient asynchronous processing and parallel execution mechanisms. Design backend services capable of processing large volumes of data with low latency and high throughput. Apply distributed systems principles to ensure application scalability, reliability, and fault tolerance. Optimize application performance, memory utilization, JVM behavior, and database interactions. Troubleshoot complex production issues involving concurrency, thread contention, memory leaks, and performance bottlenecks. Collaborate with architects, engineering teams, and business stakeholders to translate requirements into robust technical solutions. Participate in architecture discussions, technical design reviews, and code reviews. Write clean, maintainable, well-tested production-quality code. Required Technical Skills Core Java & Concurrency 8+ years of professional Java development experience. Strong hands-on experience with Java 11/17/21 or newer. Excellent understanding of Java collections, generics, streams, and functional programming. Deep knowledge of multithreading, concurrency, synchronization, and thread safety. Experience with ExecutorService, CompletableFuture, thread pools, concurrent collections, and asynchronous programming. Strong understanding of JVM internals, garbage collection, memory management, and performance tuning. Spring Boot & Microservices Extensive hands-on experience with Spring Boot and the Spring ecosystem. Proven experience designing and developing microservices-based applications. Strong knowledge of REST APIs, service-to-service communication, and API design. Understanding of distributed transactions, resilience patterns, circuit breakers, retries, and fault tolerance. Experience building scalable, highly available backend services. Performance & Distributed Systems Experience developing high-throughput, low-latency applications. Strong understanding of concurrent processing, asynchronous workflows, and event-driven architectures. Ability to identify and resolve performance bottlenecks. Experience with distributed caching, messaging, and data processing systems. Strong debugging, profiling, and production troubleshooting skills. Databases & Development Tools Strong SQL skills and experience with relational databases such as PostgreSQL, Oracle, or MySQL. Experience with database query optimization and performance tuning. Proficiency with Git, Maven/Gradle, and automated testing frameworks. Experience with CI/CD pipelines and modern software engineering practices. Preferred / Nice-to-Have Skills Experience with market data, financial data, real-time data feeds, or other data-intensive platforms. Hands-on experience with Kafka or similar event-streaming technologies. Experience with Redis or other distributed caching solutions. Familiarity with Kubernetes, Docker, and cloud platforms such as AWS. Experience with reactive programming frameworks. Understanding of messaging systems, event processing, and data ingestion pipelines. Experience building systems requiring high availability, low latency, and continuous data processing. What We//'re Looking For This is a hands-on senior engineering position, not primarily a team management or coordination role. The successful candidate should be comfortable: Writing complex Java code independently. Designing and troubleshooting multithreaded applications. Explaining concurrency concepts and their practical implementation. Building production-grade Spring Boot microservices. Solving complex performance and scalability challenges. Understanding architectural trade-offs in distributed systems. Taking technical ownership of backend components from design through production. Candidates with strong Core Java fundamentals, practical multithreading experience, and deep Spring Boot/microservices expertise will be prioritized.