Senior Java Backend Developer

We are looking for a Senior Java Backend Developer. This role is a 3 days Hybrid contract role in Mississauga. If you have all the skills please apply with a copy of your updated resume and contact details. Karat - Software Engineer – Java – Senior (C13/C14) 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. 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.

The role involves designing and optimizing high-performance backend applications specialized in batch and real-time data processing. The developer will drive the architecture of complex distributed systems and provide technical mentorship to other engineers.

Candidates need 8+ years of experience in Java-based backend architectures with expert-level knowledge of JVM, concurrency, and the Spring ecosystem. Proficiency in distributed data processing tools like Kafka and Spark, as well as CI/CD and containerization, is required.

• KubernetesPreferred
• PostgreSQLPreferred
• DockerPreferred
• Spring BootPreferred

Identified from the job description. Confirm important requirements above.

• Core Java
• Spring Boot
• Apache Kafka
• Apache Spark
• Distributed Systems
• Microservices
• JVM Performance Tuning
• Multithreading
• Hibernate
• PostgreSQL
• NoSQL
• Docker
• Kubernetes
• TDD
• RESTful APIs
• gRPC

• Software
• Technology
• Engineering
• Data & Analytics
• Consulting

Minimum experience

10+ years

Apply by

Sep 4, 2026

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