Senior Software Engineer

OKTO's continuous growth demands high-caliber candidates who can demonstrate professionalism, passion, and creativity. For those who come on board, we offer significant career advancement, challenges, and a runway for growth.
OKTO powers digital payments for every entertainment, leisure, and gaming environment. Our unified payment platform combines secure, real-world transactions with the most powerful payment technology to create immersive payment experiences for both merchants and their users.
Since 2019, OKTO has been improving payment interactions for online and retail gaming and introducing frictionless payments with its local knowledge, sector expertise, and international capabilities.
The expanding business now employs over 200 payment experts, gaming insiders, and software engineers, serving some of the most exciting international markets, including Brazil, Romania, Italy, Greece, Germany, the UK, and Spain.

Summary

As a Senior Software Engineer, you will play a key technical leadership role in architecting, designing, and developing our next-generation payment platform. This position requires deep expertise in distributed systems, Java-based microservices, and high-volume transaction processing. You will be responsible for ensuring the platform meets the highest standards of scalability, security, and reliability while working closely with product, infrastructure, and security teams. This position offers tremendous career growth and the opportunity to make a direct impact in a rapidly expanding international company.

Your responsibilities will include:

• Leading the design and architecture of complex distributed systems that handle real-time financial transactions at scale.

• Spearheading the integration of payment gateways, banks, card networks, and alternative payment methods.

• Taking a lead role in our transition to a microservices-based architecture for payments.

• Creating and maintaining high-quality, optimized code with robust unit tests and appropriate test coverage.

• Providing technical leadership, mentoring junior developers, and guiding the team in best practices and efficient coding techniques.

• Collaborating with cross-functional teams to deliver highly scalable, performant solutions.

• Driving continuous improvement initiatives, identifying bottlenecks, and optimizing the software development lifecycle.

• Collaborating with DevOps to optimize CI/CD pipelines, and monitoring strategies for production systems.

Requirements

• Excellent academic background: Bachelor's or Master's degree in Computer Engineering or a related field.

• Proven experience (7+ years) in backend software development, with at least 3 years leading teams and architecting payment systems.

• Strong understanding of payment flows, settlement, reconciliation, and fraud detection mechanisms.

• Deep knowledge of Java 11+, Spring Boot.

• Strong experience with AWS cloud services, including IAM, EC2, S3, Lambda, RDS, DynamoDB, and API Gateway.

• Hands-on experience with transaction management, database tuning (PostgreSQL, MySQL, or NoSQL stores), and high-availability strategies.

• Extensive experience with Event-Driven Software Design Patterns and complex systems architecture.

• Expertise in microservices architecture, specifically with Java 8+, Spring Boot, Spring Cloud (Netflix OSS), OAuth2 Security, and JPA ORM.

• Expertise in designing secure RESTful APIs and working with OAuth2, JWT, and SSO mechanisms.

• Advanced proficiency in Git for source control and versioning.

• Strong technical writing skills, with the ability to produce clear and concise technical requirements, design documents, and specifications.

• A proven ability to communicate complex technical concepts effectively in both Greek and English.

Benefits

Competitive remuneration package tailored to your experience.
Opportunity to work in a fast-paced, international company with a global presence.
A friendly, motivating, and challenging environment where you can thrive and continue developing your skills.
Continuous training for all your learning and development needs.
Career advancement opportunities, with structured feedback and performance reviews.
Flexible work-from-home options to ensure a healthy work-life balance.
#LI-Hybrid, #LI-Remote