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Senior Java Engineer
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- City of residence:
- Poltava
- Ready to work:
- Remote
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IGOR ZAPOROZHTSEV
Senior Java Engineer
[open contact info ](look above in the "contact info" section) | [open contact info ](look above in the "contact info" section) | Ukraine · Remote | English B2
SUMMARY
Senior Java Engineer with 5+ years of experience building backend systems across enterprise platforms.
Experienced in designing and delivering microservices, APIs, and integrations using event-driven architecture, as well as
troubleshooting production issues.
SKILLS
Languages: Java 8, 11, 17, 21
Frameworks: Spring Boot 3, Spring Cloud, Spring Security
Auth & Access: Keycloak, JWT, OAuth2, RBAC, ABAC
Databases: PostgreSQL, Elasticsearch, Neo4j, Liquibase
Messaging: Apache Kafka
API: REST (OpenAPI/Swagger), gRPC (protobuf)
Architecture: Microservices, CQRS, Event-driven, DDD, Hexagonal
Containers: Docker
Testing: JUnit 5, Mockito, Testcontainers, WireMock, AssertJ
Build Tools: Gradle, Maven
Observability: Prometheus, Grafana, Loki, Tempo, Micrometer
WORK EXPERIENCE
Mascode Mar 2025 – Apr 2026
Java Software Engineer
Investigation Management System - a microservices platform for managing structured case data with secure
collaboration, search, and analytics.
• Designed domain logic for microservices using DDD and Hexagonal Architecture in a distributed system
• Built microservices from scratch using CQRS and event-driven architecture
• Developed gRPC APIs for inter-service communication
• Implemented service communication using gRPC and Feign Client
• Implemented gRPC error handling on both client and server sides
• Implemented ABAC and RBAC authorization models across services
• Integrated Keycloak authentication and authorization with Spring Security
• Resolved production issues related to lost updates using optimistic locking
• Implemented processing of third-party client events and external data integration
• Developed API Gateway using Spring Cloud MVC for request routing across services
Stack: Java 21, Spring Boot 3, Kafka, gRPC, REST, PostgreSQL, Elasticsearch, Neo4j, Keycloak, Flowable (DMN, BPMN),
Liquibase, Docker
GlobalLogic Jul 2023 – Jun 2024
Java Software Engineer · Kyiv
Enterprise data storage management platform integrating on-premise infrastructure with AWS for policy-based storage
automation.
• Implemented an AWS Lambda-based authentication proxy for validating access tokens, enriching requests with
user context, and forwarding them to backend services.
• Built REST APIs and business logic for User Management microservices
• Improved Hibernate performance via transaction handling and persistence optimizations
• Optimized database queries using indexing and selective flush strategies
• Wrote PostgreSQL stored procedures for specific data processing tasks
• Configured Nginx as a reverse proxy with port forwarding for service routing
• Resolved service discovery latency issues and fixed a race condition in concurrent sessions
• Implemented AWS Lambda for asynchronous processing
Stack: Java 11/17, Spring Boot, Hibernate, PostgreSQL, Elasticsearch, Redis, AWS Lambda, Liquibase
SPD-Ukraine Mar 2021 – Aug 2022
Kotlin Software Engineer
Cloud-native IoT connectivity platform with built-in billing for global telecom operators (BSS/IoT domain).
• Built a billing microservice from scratch: tariffs, billing periods, call/SMS/data rating, discounts, and bonuses
• Implemented core billing and revenue calculation logic for subscription-based services
• Introduced Spring State Machine for lifecycle management of billing and subscription entities
• Integrated Kafka for real-time processing of telecom events (calls, SMS, data) for rating
• Developed and maintained REST APIs for billing/rating services
• Fixed production bugs and delivered new business features
Stack: Kotlin, Spring Boot, PostgreSQL, Kafka, Apache Ignite, Hazelcast, Hibernate, Liquibase
GlobalLogic Oct 2018 – Mar 2021
Java Software Engineer
Telecom OSS project — system for managing network equipment (shelves, ports, physical connections).
• Delivered customer-specific features for hardware management, improving product fit for individual operator
environments
• Handled production support rotation, resolving customer issues and reducing escalation time
• Fixed production bugs
Stack: Java 8/11, Spring, EJB, REST, ActiveMQ, JBoss, Weblogic, Java EE
EDUCATION
Bachelor's Degree · National Aviation University
Computerized Systems, Automatics, and Management
Senior Java Engineer
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SUMMARY
Senior Java Engineer with 5+ years of experience building backend systems across enterprise platforms.
Experienced in designing and delivering microservices, APIs, and integrations using event-driven architecture, as well as
troubleshooting production issues.
SKILLS
Languages: Java 8, 11, 17, 21
Frameworks: Spring Boot 3, Spring Cloud, Spring Security
Auth & Access: Keycloak, JWT, OAuth2, RBAC, ABAC
Databases: PostgreSQL, Elasticsearch, Neo4j, Liquibase
Messaging: Apache Kafka
API: REST (OpenAPI/Swagger), gRPC (protobuf)
Architecture: Microservices, CQRS, Event-driven, DDD, Hexagonal
Containers: Docker
Testing: JUnit 5, Mockito, Testcontainers, WireMock, AssertJ
Build Tools: Gradle, Maven
Observability: Prometheus, Grafana, Loki, Tempo, Micrometer
WORK EXPERIENCE
Mascode Mar 2025 – Apr 2026
Java Software Engineer
Investigation Management System - a microservices platform for managing structured case data with secure
collaboration, search, and analytics.
• Designed domain logic for microservices using DDD and Hexagonal Architecture in a distributed system
• Built microservices from scratch using CQRS and event-driven architecture
• Developed gRPC APIs for inter-service communication
• Implemented service communication using gRPC and Feign Client
• Implemented gRPC error handling on both client and server sides
• Implemented ABAC and RBAC authorization models across services
• Integrated Keycloak authentication and authorization with Spring Security
• Resolved production issues related to lost updates using optimistic locking
• Implemented processing of third-party client events and external data integration
• Developed API Gateway using Spring Cloud MVC for request routing across services
Stack: Java 21, Spring Boot 3, Kafka, gRPC, REST, PostgreSQL, Elasticsearch, Neo4j, Keycloak, Flowable (DMN, BPMN),
Liquibase, Docker
GlobalLogic Jul 2023 – Jun 2024
Java Software Engineer · Kyiv
Enterprise data storage management platform integrating on-premise infrastructure with AWS for policy-based storage
automation.
• Implemented an AWS Lambda-based authentication proxy for validating access tokens, enriching requests with
user context, and forwarding them to backend services.
• Built REST APIs and business logic for User Management microservices
• Improved Hibernate performance via transaction handling and persistence optimizations
• Optimized database queries using indexing and selective flush strategies
• Wrote PostgreSQL stored procedures for specific data processing tasks
• Configured Nginx as a reverse proxy with port forwarding for service routing
• Resolved service discovery latency issues and fixed a race condition in concurrent sessions
• Implemented AWS Lambda for asynchronous processing
Stack: Java 11/17, Spring Boot, Hibernate, PostgreSQL, Elasticsearch, Redis, AWS Lambda, Liquibase
SPD-Ukraine Mar 2021 – Aug 2022
Kotlin Software Engineer
Cloud-native IoT connectivity platform with built-in billing for global telecom operators (BSS/IoT domain).
• Built a billing microservice from scratch: tariffs, billing periods, call/SMS/data rating, discounts, and bonuses
• Implemented core billing and revenue calculation logic for subscription-based services
• Introduced Spring State Machine for lifecycle management of billing and subscription entities
• Integrated Kafka for real-time processing of telecom events (calls, SMS, data) for rating
• Developed and maintained REST APIs for billing/rating services
• Fixed production bugs and delivered new business features
Stack: Kotlin, Spring Boot, PostgreSQL, Kafka, Apache Ignite, Hazelcast, Hibernate, Liquibase
GlobalLogic Oct 2018 – Mar 2021
Java Software Engineer
Telecom OSS project — system for managing network equipment (shelves, ports, physical connections).
• Delivered customer-specific features for hardware management, improving product fit for individual operator
environments
• Handled production support rotation, resolving customer issues and reducing escalation time
• Fixed production bugs
Stack: Java 8/11, Spring, EJB, REST, ActiveMQ, JBoss, Weblogic, Java EE
EDUCATION
Bachelor's Degree · National Aviation University
Computerized Systems, Automatics, and Management
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The candidate's resume is posted at https://www.work.ua/resumes/19116963/