Giorgos is available for hire
Hire GiorgosGiorgos Mitaros
Verified Expert in Engineering
Back-end Engineer and Developer
Athens, Central Athens, Greece
Toptal member since March 7, 2025
Bio
Giorgos is a senior back-end engineer with seven years of experience building scalable systems with Java, Spring Boot, Kafka, and Kubernetes. He specializes in microservices, event-driven architectures, and high-throughput platforms, delivering clean, reliable solutions for complex production environments.
Portfolio
Endeavor - Streaming DBA Dice Technology
Java, Docker, Amazon Web Services (AWS), Spring Boot, Kubernetes, Terraform...
OPAP
Apache Kafka, Docker, Distributed Systems, Java, Jira, RabbitMQ, PostgreSQL...
Accenture
Docker, Java, Kubernetes, Jenkins, SQL Server 2019, Spring Boot, Spring Batch...
Experience
- Java - 5 years
- Jira - 5 years
- Spring Boot - 5 years
- RabbitMQ - 5 years
- Kubernetes - 4 years
- Docker - 3 years
- PostgreSQL - 3 years
- Apache Kafka - 2 years
Preferred Environment
Java, Spring Boot, Apache Kafka, RabbitMQ, Kubernetes, Docker, Slack, PostgreSQL, IntelliJ IDEA, Jira
The most amazing...
...thing I created is a real-time event-processing system that handles 15+ million Kafka messages daily for high-volume betting and financial calculations.
Work Experience
Senior Java Developer – Global Streaming Platform
2025 - 2026
Endeavor - Streaming DBA Dice Technology
- Developed and maintained Java and Spring Boot services supporting a global OTT streaming platform used to deliver live and on-demand digital content.
- Implemented back-end features and API integrations within a distributed microservices architecture deployed across AWS-based production environments.
- Improved and supported containerized services running on Kubernetes, using Docker-based development and deployment workflows across multiple environments.
- Contributed to infrastructure and application delivery workflows using Terraform, supporting repeatable provisioning and configuration of cloud resources.
- Investigated and resolved back-end defects across interconnected streaming-platform services, improving application reliability and production stability.
- Collaborated with engineers across back-end, front-end, mobile, infrastructure, and product teams to deliver functionality across a multi-platform streaming ecosystem.
- Worked within a large existing Java codebase, reviewing implementations, diagnosing cross-service issues, and delivering maintainable production-ready changes.
Technologies: Java, Docker, Amazon Web Services (AWS), Spring Boot, Kubernetes, Terraform, Back-end
Senior Software Engineer
2022 - 2025
OPAP
- Processed high-volume betting data of 6+ million bets daily with Kafka to calculate real-time gross gaming revenue per player, enhancing financial reporting accuracy.
- Implemented new features on communication services for campaigns, handling push notifications, SMS, and Viber messages to over 200,000 customers, increasing campaign effectiveness.
- Orchestrated platform scalability with Kubernetes and integrated Azure services for robust back-end solutions, achieving 99.9% uptime.
- Conducted proof of concept (POC) on Quarkus, exploring performance improvements for Java applications.
- Improved bonus mechanisms in the player account management platform by developing new features using Java, Spring Boot, and Oracle Database, enhancing player engagement and retention.
- Migrated the monolithic application to a microservices architecture, transitioning from WildFly server to Spring Boot microservices, improving scalability and maintainability.
- Developed an event processing service with a team, leveraging RabbitMQ, Azure Functions, and Azure Event Hubs to unify event payloads for downstream processing.
- Implemented real-time analytics using Azure Stream Analytics to generate informational events such as user inactivity after login or deposit behaviors, enabling targeted marketing campaigns and increasing user activity by 25%.
- Integrated with Salesforce and gamification platforms, providing enriched event data to trigger personalized bonuses and gamification tasks, boosting customer engagement.
Technologies: Apache Kafka, Docker, Distributed Systems, Java, Jira, RabbitMQ, PostgreSQL, Kubernetes, Redis, Azure Functions, Azure Stream Analytics, Spring Boot, Software Engineering, Software Development, Back-end, Back-end Development, Azure, Proof of Concept (POC), Quarkus, Spring, Oracle Database, Microservices, Microservices Architecture, WildFly, Spring Microservice, Azure Event Hubs, Salesforce, Gamification, SQL, REST APIs, API Integration, Event-driven Architecture, Event-driven Design (EDD), Prompt Engineering, APIs
Application Development Senior Analyst
2022 - 2022
Accenture
- Led the development of the stock and bond purchasing process digitalization through web banking, increasing online investment transactions.
- Collaborated with business analysts, QAs, and cross-functional teams to deliver high-quality software solutions on time.
- Enhanced database efficiency and query execution speed by optimizing SQL scripts, structuring tables, and adding strategic indexing, improving application responsiveness by 35%.
Technologies: Docker, Java, Kubernetes, Jenkins, SQL Server 2019, Spring Boot, Spring Batch, React, Redis, App Development, Software Development, Back-end, Back-end Development, SQL, REST APIs, API Integration, APIs
Application Development Analyst
2021 - 2022
Accenture
- Maintained automated regression tests and Jenkins pipelines, allowing continuous integration and reducing deployment times by 50%.
- Provided technical estimates for new projects and mentored junior developers in software patterns, Kubernetes, and microservices.
- Developed a multi-business account management system, allowing seamless access to company accounts.
Technologies: IntelliJ IDEA, Java, Jira, Kubernetes, RabbitMQ, Spring Boot, React, App Development, Software Development, Back-end, Back-end Development, Jenkins, Jenkins Pipeline, Continuous Integration (CI), Microservices, Microservices Architecture, SQL, REST APIs, APIs
Application Development Associate
2019 - 2021
Accenture
- Designed and implemented full-stack features for an omnichannel banking platform using Java, Spring Boot, RabbitMQ, and React, improving customer engagement and operational efficiency.
- Ensured software reliability by writing unit and integration tests, enhancing system stability.
- Collaborated with cross-functional teams in an Agile environment to deliver scalable, high-performance banking solutions.
Technologies: IntelliJ IDEA, Java, Jira, Kubernetes, RabbitMQ, Spring Boot, App Development, Software Development, Back-end, Back-end Development, Full-stack, Full-stack Development, Spring, React, Unit Testing, Integration Testing, Software Testing, Agile, SQL, REST APIs, APIs
Experience
Real-time Event Processing System for a Betting Platform
Designed and implemented a real-time event processing system for a large-scale betting platform, handling 15+ million Kafka messages daily.
The system processed critical user events such as logins, bet placements, and transactions. Using Kafka, RabbitMQ, and Spring Boot, I developed a microservices-based architecture to ensure scalability and fault tolerance.
The solution transformed raw event data into structured payloads, integrated with Azure Event Hub, and provided real-time analytics. This project significantly improved data accuracy and reduced latency in financial reporting, enhancing overall system reliability.
The system processed critical user events such as logins, bet placements, and transactions. Using Kafka, RabbitMQ, and Spring Boot, I developed a microservices-based architecture to ensure scalability and fault tolerance.
The solution transformed raw event data into structured payloads, integrated with Azure Event Hub, and provided real-time analytics. This project significantly improved data accuracy and reduced latency in financial reporting, enhancing overall system reliability.
KleidiFlow – Hospitality Operations and Property Management SaaS
https://kleidiflow.comKleidiFlow is a multi-tenant hospitality operations SaaS built for independent hotels, studios, guesthouses, and boutique properties.
I designed and developed the platform to replace fragmented spreadsheets and manual workflows with a centralized system for reservations, availability, guest management, check-ins, payments, and reconciliation. The product uses a React and Next.js mobile-first interface with a Java and Spring Boot back end, PostgreSQL, and Supabase authentication. I implemented tenant isolation, role-based access, audit trails, guest profiles and history, reservation concurrency controls, pricing rules, payment ledgers, CSV interoperability, self-check-in workflows, and integration-oriented architecture using ports/adapters and transactional patterns. The platform is designed to simplify daily property operations while remaining lightweight enough for smaller hospitality businesses.
I designed and developed the platform to replace fragmented spreadsheets and manual workflows with a centralized system for reservations, availability, guest management, check-ins, payments, and reconciliation. The product uses a React and Next.js mobile-first interface with a Java and Spring Boot back end, PostgreSQL, and Supabase authentication. I implemented tenant isolation, role-based access, audit trails, guest profiles and history, reservation concurrency controls, pricing rules, payment ledgers, CSV interoperability, self-check-in workflows, and integration-oriented architecture using ports/adapters and transactional patterns. The platform is designed to simplify daily property operations while remaining lightweight enough for smaller hospitality businesses.
Education
2012 - 2019
Engineering Diploma in Computer Science and Engineering
University of Ioannina - Ioannina, Greece
Skills
Libraries/APIs
REST APIs, React, Jenkins Pipeline
Tools
RabbitMQ, Slack, IntelliJ IDEA, Jira, Jenkins, WildFly, Terraform
Languages
Java, Python, SQL
Frameworks
Spring Boot, Spring, Spring Batch, Spring Microservice, Next.js
Paradigms
Event-driven Architecture, Event-driven Design (EDD), Microservices, Microservices Architecture, Gamification, App Development, Continuous Integration (CI), Unit Testing, Software Testing, Agile
Platforms
Apache Kafka, Azure Event Hubs, Kubernetes, Docker, Azure Functions, Azure, Oracle Database, Salesforce, Amazon Web Services (AWS)
Storage
PostgreSQL, SQL Server 2019, Redis
Other
APIs, API Integration, Prompt Engineering, Distributed Systems, Azure Stream Analytics, Computer Science, Software Engineering, Software Development, Back-end, Back-end Development, Proof of Concept (POC), Quarkus, Full-stack, Full-stack Development, Integration Testing, Supabase, SaaS
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