Senior Java Backend Engineer

Citi; Mississauga; Hybrid; CAD 121,000 - 171,000; Full time

Job summary

Citi is seeking a Senior Java Backend Engineer to design high-performance, event-driven systems at global scale. You will architect reactive microservices, integrate real-time data streams, and ensure engineering quality across a modern Java stack.

You will mentor engineers, collaborate with product and architecture teams, and contribute to features that impact Citi’s clients worldwide. This full-time role offers hybrid work arrangements in a major tech hub.

Qualifications

• Experience building and scaling Java applications.
• Proficiency with Spring WebFlux, Project Reactor, or RxJava.
• Experience with Apache Kafka and real-time data streams.
• NoSQL data modelling with MongoDB and search with Elasticsearch.
• Strong unit testing with JUnit and code coverage.

Responsibilities

• Build and deploy asynchronous, event-driven microservices in Java.
• Design reactive backend services using Spring WebFlux and reactive libraries.
• Develop real-time event streaming pipelines with Kafka.
• Engineer search/analytics with Elasticsearch for large data sets.
• Architect and optimise MongoDB data persistence.
• Lead test-driven development and code reviews to ensure quality.
• Mentor mid-level engineers and promote coding standards.
• Collaborate with product, infra, and architecture teams on new features.

Skills

Java backend

Reactive programming

Spring WebFlux

Kafka

MongoDB

Elasticsearch

JUnit

Git workflows

CI/CD

Education

Bachelor’s degree

Master’s degree (preferred)

Tools

Docker

Kubernetes

Job description

Citi's Technology division is looking for a Senior Java Backend Engineer to design and deliver the high-performance, event-driven systems that underpin financial services at global scale. In this role, you will architect and build reactive microservices, integrate real-time data streams, and drive engineering quality across a modern Java stack. You will collaborate closely with product managers, frontend engineers, and architects to shape solutions that have direct impact on Citi's clients and operations worldwide.

Responsibilities

• Build and deploy asynchronous, event-driven microservices in Java, ensuring high availability and performance at scale.
• Design reactive backend services using Spring WebFlux, Project Reactor, and RxJava to meet demanding throughput and latency requirements.
• Develop and maintain real-time event streaming pipelines using Apache Kafka to power data-driven features across the platform.
• Engineer search and analytics capabilities using Elasticsearch to surface fast, accurate insights from large data sets.
• Architect and optimise data persistence solutions in MongoDB, ensuring efficient storage and retrieval of application data.
• Champion code quality by leading test-driven development practices, writing comprehensive JUnit test suites, and guiding teams through rigorous code reviews.
• Mentor mid-level engineers and analysts, establishing coding standards and sharing knowledge to strengthen overall team capability.
• Partner with product, infrastructure, and architecture teams to deliver new features and define system enhancements aligned to business goals.

Required Qualifications & Skills

• 6–10 years of backend software development experience, with a demonstrable focus on building and scaling Java applications.
• Deep proficiency in Java (8+), including functional programming with Lambdas and reactive paradigms using Spring WebFlux, Project Reactor, or RxJava.
• Hands-on experience building and integrating event streaming systems with Apache Kafka.
• Solid command of MongoDB for NoSQL data modelling and Elasticsearch for search and analytics implementations.
• Expert-level application of test-driven development using JUnit, with strong discipline around unit testing and code coverage.
• Proficiency in Git-based collaborative workflows, including pull requests, code reviews, and branching strategies such as GitFlow.
• Familiarity with CI/CD pipeline design to support automated testing and continuous deployment processes.

Beneficial Skills & Qualifications

• Experience containerising and orchestrating applications using Docker and Kubernetes.
• Familiarity with cloud platforms such as AWS, Azure, or GCP.
• Knowledge of additional NoSQL databases beyond MongoDB.
• Open-source contributions that demonstrate technical depth and community engagement.
• Background working in agile, fast-paced engineering environments with iterative delivery cycles.

Education

• Bachelor’s degree/University degree or equivalent experience
• Master’s degree preferred

What We Offer

At Citi, you will work on backend systems that operate at global scale, supporting financial services used by millions of clients worldwide. We invest in our engineers — providing the tools, challenges, and environment to do meaningful, high-impact work.

• Hybrid working model, with 3 days in the office and 2 days working remotely, giving you flexibility while staying connected to your team.
• Exposure to complex, large-scale engineering challenges across a modern stack including Apache Kafka, MongoDB, Elasticsearch, and reactive Java frameworks.
• Opportunities to grow technically and lead — mentoring engineers, defining standards, and influencing architectural decisions at a global institution.
• Access to structured learning and development programmes to deepen your technical expertise and accelerate your career progression.
• Competitive compensation package with financial wellbeing support and access to employee assistance programmes.
• A collaborative engineering culture with global reach, working alongside specialists across technology, product, and architecture.

This job description provides a high-level review of the types of work performed. Other job-related duties may be assigned as required.

• Strong understanding of data structures, algorithms, and object-oriented design principles.
• Experience with RESTful API design and development.
• Familiarity with cloud platforms (e.g., AWS, Azure, GCP) is a plus.
• Excellent problem-solving, analytical, and debugging skills.
• Ability to work independently and as part of a collaborative team.

Job Family Group

Technology

Job Family

Applications Development

Time Type

Full time

Primary Location Full Time Salary Range

$120,800.00 - $170,800.00

Most Relevant Skills

Please see the requirements listed above.

Other Relevant Skills

For complementary skills, please see above and/or contact the recruiter.

Automated Processing and AI

We use automated processing, including artificial intelligence, for our legitimate business interests (or our reasonable and appropriate business purposes) to identify and align the candidate's skills and abilities with a specific job opening. Additionally, if you so choose, or consent, we can match your skills and abilities to other suitable roles at Citi.

Importantly, all our hiring processes and decisions, including determining your suitability for a role, are conducted, checked, and decided by individuals. Our automated processing and AI do not involve relying on automatic or autonomous decision-making. Please refer to any Jurisdictional Considerations, with specific provisions for your country (where relevant) for further details.

Job opening information

This job opening is for an existing job vacancy.

Equal Opportunity

Citi is an equal opportunity employer, and qualified candidates will receive consideration without regard to their race, color, religion, sex, sexual orientation, gender identity, national origin, disability, status as a protected veteran, or any other characteristic protected by law.

Accessibility

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EEO Policy

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