Java Software Engineer

Mississauga, ON
Hybrid
Posted Oct 8, 2026
1 position

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Employment type: Contract
Experience level: Senior · 5+ years
Posting language: English
Working hours: 40 hours per week
Office presence: 3 days per week
Seniority: Mid-Senior level
Application method: Direct apply is available

Job summary

Design, build, and optimize scalable Java backend systems for batch and real-time data processing, including leading delivery of complex distributed-system initiatives. Diagnose performance, memory, and concurrency issues; uphold testing and code-quality practices; and provide technical mentorship to fellow engineers.

Job details

Java Developer Mississauga ON – 3days/week onsite Contract to Hire – 2 rounds interview first virtual second onsite in Mississauga Position Overview We are seeking a highly skilled and passionate Senior Java Backend Developer to join our engineering team as a Senior Individual Contributor. In this role, you will be responsible for designing, building, and optimizing high-performance, robust, and scalable backend applications specialized in batch and real-time data processing. As a senior technical leader with a strong programming background, you will drive the architecture and implementation of complex distributed systems. You will play a crucial role in analyzing system requirements, designing data flows, and ensuring clean, maintainable, and highly efficient code. This role demands deep technical expertise in Core Java, concurrency, memory management, and modern distributed data frameworks, without the burden of people management responsibilities. [ Key Responsibilities Systems Analysis & Architecture: Analyze complex business requirements and translate them into highly scalable, reliable, and secure backend systems designs. Evaluate trade-offs between different data architecture patterns (e.g., microservices vs. event-driven). Hands-on Programming: Write high-quality, production-ready, and performant Java code. Leverage advanced software engineering principles such as Object-Oriented Programming (OOP), SOLID design principles, and design patterns. Technical Project Delivery: Lead the technical implementation and delivery of critical, complex backend and data-processing initiatives. Partner with cross-functional teams to ensure successful project deployment from conception through production. Subject Matter Expertise (SME): Act as the resident Subject Matter Expert (SME) in high-throughput data processing, stream processing, or JVM performance tuning. Provide guidance on industry best practices and emerging backend technologies. Performance Optimization: Diagnose, profile, and resolve complex performance bottlenecks, memory leaks, and concurrency issues in high-volume distributed environments. Quality Assurance & Best Practices: Champion code quality through Test-Driven Development (TDD), comprehensive unit/integration testing, and rigid code review standards. Mentorship: Provide technical mentorship and architectural guidance to other engineers on the team, fostering a culture of technical excellence and clean code. Technical Skills & Qualifications Required Qualifications: Experience: 8+ years of professional experience in application development or systems analysis, with a heavy emphasis on Java-based backend architectures. Core Java Mastery: Deep, expert-level understanding of Core Java (Java 11/17/21), including advanced multithreading, concurrency models, Java memory model (JVM garbage collection, heap analysis), and Collections API. Data Processing & Streaming: Extensive hands-on experience building distributed data processing systems, ETL pipelines, and real-time streaming architectures using tools like Apache Kafka, Apache Spark, Flink, or Hadoop. Framework Expertise: Strong experience with the Spring Ecosystem (Spring Boot, Spring Cloud, Spring Data, Spring Security) and ORM frameworks (Hibernate/JPA). Database Management: Proficiency in designing schemas and writing optimized queries for both relational databases (e.g., PostgreSQL, MySQL, Oracle) and NoSQL stores (e.g., Cassandra, MongoDB, Redis). Distributed Systems: Comprehensive understanding of distributed system design patterns, consensus protocols, caching strategies, and API design (RESTful APIs, gRPC). CI/CD & DevOps: Practical experience with containerization (Docker, Kubernetes), continuous integration/continuous deployment tools (Jenkins, GitLab CI, or GitHub Actions), and infrastructure-as-code principles. Testing: Strong advocate for testing frameworks such as JUnit, Mockito, and integration testing tools. Preferred Qualifications: Experience with cloud platforms (AWS, Azure, or GCP), specifically managed database and container services. Experience in financial services, banking technology, or large-scale enterprise transaction systems. Familiarity with Unix/Linux environments, shell scripting, and network configurations.

What you’ll do

Requirements

Requires 8+ years of application development or systems analysis experience, with expert-level Core Java and hands-on experience in distributed data processing, streaming, Spring, databases, and distributed systems. Also requires practical experience with containerization, CI/CD, and testing; cloud platforms and financial-services experience are preferred.