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Sr. Core Java Developer W2

Congensys Corp.Menlo Park, CA🇺🇸United StatesPosted 13 Aug 2026

Quick Overview

Work Type
On Site
Level
Mid Senior

Job Description

Sr. Core Java Developer / Lead

Location: Alpharetta, GA / Menlo Park, CA
Job Type: Contract
Employment Type: W2 Only
Work Arrangement: Onsite / Local Candidates Only
Experience: 10+ Years

Job Description

We are seeking a highly skilled Sr. Core Java Developer / Lead with 10+ years of experience in Java software development to design, develop, test, and maintain high-performance, scalable, and reliable enterprise applications.

The ideal candidate will have strong expertise in Core Java, OOP, multithreading, concurrency, data structures, design patterns, JVM, memory management, REST APIs, and enterprise backend development.

Key Responsibilities

  • Design, develop, test, and maintain applications using Core Java.

  • Write clean, efficient, reusable, and maintainable code.

  • Apply OOP principles, design patterns, and best coding practices.

  • Develop multithreaded and highly concurrent applications.

  • Work with Java Collections, Generics, Streams, Lambda expressions, and exception handling.

  • Develop and consume RESTful APIs and backend services.

  • Build modular, scalable, and high-performance application components.

  • Implement business logic, validation, error handling, and transaction management.

  • Work with relational and NoSQL databases.

  • Write and optimize SQL queries and database interactions.

  • Troubleshoot production issues, memory leaks, performance bottlenecks, and application defects.

  • Participate in code reviews and technical design discussions.

  • Develop unit and integration tests using JUnit, Mockito, or equivalent tools.

  • Integrate applications with CI/CD pipelines.

  • Collaborate with architects, developers, QA, DevOps, product managers, and business stakeholders.

  • Participate in Agile/Scrum ceremonies and sprint activities.

  • Support application deployment, monitoring, and production issue resolution.

Required Skills

  • 10+ years of professional Java development experience.

  • Strong hands-on experience with Core Java / Java SE.

  • Strong knowledge of:

    • Object-Oriented Programming

    • Collections Framework

    • Generics

    • Exception Handling

    • Multithreading & Concurrency

    • Java I/O & NIO

    • Streams & Lambda Expressions

    • JVM Architecture

    • Memory Management & Garbage Collection

    • Serialization & Reflection

  • Strong Data Structures and Algorithms knowledge.

  • Experience with Java 8 or later.

  • Experience developing RESTful APIs and backend services.

  • Strong SQL and database development experience.

  • Experience with JDBC and ORM concepts.

  • Experience with Spring / Spring Boot.

  • Experience with Maven or Gradle.

  • Experience with Git.

  • Experience with JUnit / Mockito.

  • Strong debugging and problem-solving skills.

  • Experience working in Agile/Scrum environments.

Preferred Skills

  • Java 11, 17, 21 or later.

  • Spring MVC, Spring Data, Spring Security.

  • Microservices architecture.

  • Kafka, RabbitMQ, JMS, or ActiveMQ.

  • Docker and Kubernetes.

  • AWS, Azure, or Google Cloud.

  • MongoDB, Redis, Cassandra, or DynamoDB.

  • Distributed systems and event-driven architecture.

  • Caching technologies.

  • CI/CD tools such as Jenkins, GitHub Actions, GitLab CI, or Azure DevOps.

  • Application monitoring and observability tools.

  • Performance testing and profiling.

  • Linux/Unix and shell scripting.

  • Secure coding and application security practices.

Education

Bachelor’s degree in Computer Science, Engineering, Information Technology, or a related field preferred.

Candidate Requirements

Local candidates only – Alpharetta, GA or Menlo Park, CA
W2 candidates only.
Candidates should have strong hands-on Core Java development experience and be available to work from the specified location.

Interested candidates: Please send your updated resume along with your current location, work authorization, and contact information.

Skills

Docker
DynamoDB
Microservices
MongoDB
SQL
Shell
Spring
Spring Boot
AWS
Scrum
Agile
Azure
Cassandra
Git
GitHub Actions
GitLab CI
Google Cloud
JUnit
Java
Jenkins
Kafka
Kubernetes
REST
RabbitMQ
Redis

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