Back End Developer

SD Solutions; Warszawa; On-site; PLN 180,000 - 280,000; Full time

Job summary

NDA, FinTech in Warsaw is seeking a talented Backend Engineer to design, develop, and maintain robust server-side systems powering our financial technology products. You will build scalable, secure, and high-performance backend services, handling data processing, API development, and integration with diverse systems in a fast-paced fintech environment.

Collaborate with frontend, product, QA, and DevOps to translate business needs into solid technical solutions.

Qualifications

• 7+ years of professional backend experience with scalable server-side apps.
• Strong Java or Kotlin expertise and modern backend patterns.
• Experience with microservices, distributed systems, and cloud platforms.

Responsibilities

• Design and implement scalable backend architecture, services and APIs.
• Develop high-quality, secure backend code with focus on performance.
• Build RESTful APIs (and GraphQL) for mobile and web apps.
• Manage databases (SQL/NoSQL) and ensure data integrity.
• Collaborate with cross-functional teams to translate requirements.
• Participate in code reviews and test automation.
• Monitor, troubleshoot, and contribute to on-call rotations.

Skills

Java

Kotlin

Microservices

Distributed systems

Relational DB

NoSQL

Kafka

RabbitMQ

AWS

Spring

Education

B.Sc. in Computer Science

Tools

Docker

Kubernetes

Git

CI/CD

Job description

On behalf of NDA, FinTech, SD Solutions is looking for a talented Backend Engineer.

As a Backend Engineer, you will design, develop, and maintain robust server-side systems that power our financial technology products. You will focus on building scalable, secure, and high-performance backend services, handling critical data processing, API development, and integration with various systems. Working closely with frontend engineers, product managers, and other stakeholders, you will contribute to delivering reliable solutions that enhance user experience and support key business objectives in a fast-paced fintech environment.

Responsibilities

• Design and implement scalable backend architecture, services, and APIs for core financial products and features.
• Develop high-quality, maintainable server-side code with a strong emphasis on performance, reliability, and security.
• Build and maintain RESTful APIs (and potentially GraphQL) to support mobile and web applications.
• Manage databases (relational and non-relational), optimize queries, and ensure data integrity and consistency.
• Collaborate with cross-functional teams (frontend, product, QA, DevOps) to translate business requirements into technical solutions.
• Participate in code reviews, write unit/integration tests, and contribute to improving engineering practices.
• Monitor system performance, troubleshoot production issues, and participate in on-call rotations as needed.
• Contribute to continuous improvement by refactoring legacy code, adopting best practices, and staying current with relevant technologies.

Requirements

• 7+ years of professional experience as a Backend Engineer (or similar role) building scalable server-side applications.
• Strong proficiency in at least one modern backend language such as Java or Kotlin.
• Solid experience with microservices architecture and distributed systems.
• Hands\u2011on experience with relational databases (e.g., MySQL, PostgreSQL) and non-relational databases (e.g., MongoDB, DynamoDB).
• Experience with AI tools and a strong interest in continuously exploring and applying them in everyday work are highly valued.
• Familiarity with message queue / streaming technologies such as Kafka, RabbitMQ, SQS, or similar.
• Good understanding of cloud platforms (preferably AWS or similar), including services for compute, storage, and networking.
• Experience building secure, high-performance APIs and handling sensitive data (especially valuable in fintech).
• Strong problem\u2010solving skills, attention to detail, and ability to work effectively in a fast-paced, collaborative environment.
• Excellent communication skills and fluency in English.
• B.Sc. in Computer Science or equivalent practical experience.

Preferred Experience

• Expertise in Spring Framework (Spring Boot).
• Experience with fintech or payment processing systems, compliance requirements (e.g., PCI DSS), or secure transaction handling.
• Familiarity with containerization (Docker) and orchestration (Kubernetes).
• Knowledge of CI/CD pipelines and infrastructure as code.
• Exposure to modern development tools and practices (e.g., Git, automated testing, observability tools).

About the company

NDA, FinTech, builds financial technology for real life. Our technology eases the stress of paying for life’s expenses by giving people more options on how and when they pay. Founded in 2016, NDA, FinTech offers a next-generation, no-fee credit card that can be managed through a powerful mobile app, as well as a point-of-sale payment option available at more than 25,000 service locations, including auto dealership service centers, optical practices, dentist offices, veterinary clinics, and specialty healthcare services

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