Oleksandr

Oleksandr Galkin
Senior Java Backend Engineer
Email [відкрити контакти](див. вище в блоці «контактна інформація»)
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Location Kyiv, Ukraine
GitLab gitlab.com/kvaka313

SUMMARY
Backend engineer with 9+ years of production Java experience, currently on Java 25 and Spring Boot 4. Designs and builds event-driven microservices and data pipelines with Kafka, PostgreSQL, ClickHouse and Redis, running on Kubernetes and AWS. Takes services from architecture decisions and implementation through test strategy and CI/CD to production troubleshooting; reviews code and mentors new engineers. Works in Agile teams (Scrum/Kanban). PhD in Mathematical Physics; taught programming as an Associate Professor at Taras Shevchenko National University of Kyiv (2001–2023).
CORE COMPETENCIES
• Event-driven systems — Kafka, AWS SQS/SNS/Lambda; Outbox, Saga and change data capture (CDC) patterns.
• Technical leadership — architecture decisions, code review, mentoring new team members.
• Modern Java — Java 25 (records, sealed types, pattern matching, virtual threads); Spring Boot 4 migrations.
• Test strategy — real-infrastructure integration tests (Testcontainers, WireMock), minimal mocking, quality gates.
• Data — PostgreSQL, ClickHouse, Redis; schema evolution with Liquibase, including automated rollback tests.
• Production reliability — connection pools, concurrency defects, resource leaks, multi-tenant routing.
• Delivery — Gradle, CI/CD (Jenkins, GitLab CI), Docker, Kubernetes.
• Security — SBOM (CycloneDX), Keycloak custom plugins, applied cryptography.
TECHNICAL SKILLS
• Languages: Java 25 (Core, Multithreading, Concurrency), Kotlin, Python 3, SQL, Bash; C++, JavaScript.
• Frameworks & APIs: Spring Boot 4, Spring Core / MVC / Data / AOP / HATEOAS, JPA, Hibernate, jOOQ, JDBC, Liquibase; REST, GraphQL, WebSockets.
• Data & messaging: PostgreSQL / PostGIS, ClickHouse, Redis, DynamoDB; Apache Kafka, AWS SQS/SNS.
• Cloud & observability: AWS (Lambda, SQS, SNS, S3, CloudFront, CloudFormation, CloudWatch), Docker, Kubernetes, Datadog.
• Build, CI/CD & testing: Gradle, Maven, Jenkins, GitLab CI, Git, JUnit, Testcontainers, WireMock, JaCoCo, Checkstyle.
• Security & supply chain: SBOM generation with CycloneDX; Keycloak: developed a custom SPI provider exposing an additional REST endpoint (JAX-RS, RealmResourceProvider); applied cryptography (AES/DES, RSA, ElGamal, Diffie–Hellman, cryptographic hashing).
• Architecture & practices: microservices, event-driven architecture, Outbox, Saga, CDC, GRASP/GoF, UML; Agile (Scrum/Kanban), code review, AI-assisted development (Claude).
PROFESSIONAL EXPERIENCE
Spribe — Java DeveloperJanuary 2024 – Present
Tech stack: Java 25, Spring Boot 4, Spring Data, Hibernate, PostgreSQL, ClickHouse, Kafka, Redis, AWS S3, AWS CloudFront, AWS CloudWatch, Docker, Kubernetes, Gradle, Liquibase, Testcontainers
• Developed the asset library — the admin panel’s file manager on AWS S3 and CloudFront (folders, uploads with progress tracking, downloads, renames); made concurrent access safe with read/write locks and atomic updates of the folder index, and sped up S3 operations with a single shared client.
• Implemented integration with the core service via ClickHouse, including a dual-path data layer for operator data (JPA/PostgreSQL and ClickHouse) with integration tests for both paths.
• Built Kafka/S3 export flows deployed to Kubernetes; fixed defects in streaming Excel exports across 12+ export types, including silent row loss and broken sheet rollover.
• Drove the upgrade to Java 25 and Spring Boot 4, including the migration to Jackson 3: reduced legacy dependencies and resolved context-loading and serialization incompatibilities.
• Diagnosed and resolved HikariCP connection-pool exhaustion and multi-tenant datasource routing defects.
• Extended role-based access control with new permissions delivered as versioned Liquibase migrations; built automated rollback tests for schema changes.
• Built integration test suites on real infrastructure (Testcontainers with PostgreSQL, ClickHouse and LocalStack S3; WireMock for external HTTP services) with minimal mocking; stabilized the suite by fixing an out-of-memory failure in the shared Spring test context, flaky tests and port collisions.
• Enforced code-quality gates (Checkstyle, JaCoCo coverage thresholds) in the Gradle build to standardize quality across the team, and closed coverage gaps after the move to Java 25.
Intellias (DigitallyInspired) — Java DeveloperJune 2023 – January 2024
Tech stack: Java, Kotlin, Spring Boot, Spring Data, Hibernate, PostgreSQL, DynamoDB, Kafka, AWS SQS/Lambda/CloudWatch, GraphQL, Datadog, Docker, Kubernetes
• E-commerce: developed backend services in Java and Kotlin on Spring Boot; built GraphQL APIs over PostgreSQL; implemented event-driven integration through Kafka; monitored services with Datadog.
• Aviation: developed Spring MVC services with event-driven processing on AWS SQS and Lambda, monitored with CloudWatch.
• Deployed services to Kubernetes.
EPAM Systems — Java DeveloperMay 2019 – May 2023
Tech stack: Java, Spring, Hibernate, ANTLR 4, MuleSoft, Apache Camel, Drupal
• Backend development in Java with Spring and Hibernate for enterprise clients: Equifax and London Stock Exchange Group (LSEG).
• System integration via MuleSoft and Apache Camel (limited Camel experience); Drupal-based platform development.
Intapp — Java DeveloperJune 2017 – May 2019
Tech stack: Spring Boot, Kafka, PostgreSQL, AWS, Docker, Kubernetes, CycloneDX
• Designed and developed microservices with Kafka-based messaging on PostgreSQL, deployed to AWS and Kubernetes.
• Generated CycloneDX SBOMs in the build for dependency inventory and software supply-chain visibility.
Msystem Technology — Java DeveloperJanuary 2017 – June 2017
Tech stack: Spring Boot, Spring Data, Hibernate, PostgreSQL, Kafka, Docker
• Backend development on Spring Boot, Spring Data and Hibernate over PostgreSQL with Kafka integration.
TEACHING
Taras Shevchenko National University of Kyiv — Associate ProfessorMarch 2001 – 2023
Faculty of Computer Science and Cybernetics
• Taught Java, Spring, Hibernate, Ruby on Rails and Django; main courses: Object-Oriented Programming (C++, Java, Python, Ruby), Programming Technologies, Abstract Algebra, Functional Programming.
PROJECTS
• geocore — geocoding microservice on Java 25, Spring Boot 4 and PostGIS: address matching, autocomplete, “did you mean” suggestions, points of interest and zone geometry queries. gitlab.com/kvaka313/geocore
• Self-hosted LLM answer engine — built a retrieval-augmented generation (RAG) system: Qwen3-30B-A3B served with vLLM (tensor parallelism across two GPUs), web retrieval through SearXNG, Infinity-based embeddings, and a FastAPI orchestration service in Python.
• Earlier startup work — Android app for real-time personalized gesture recognition (DTW over accelerometer and gyroscope data); performance-approximation module for computer systems based on piecewise-linear regression.
EDUCATION
Institute of Mathematics of the National Academy of Sciences of Ukraine1996 – 1999
PhD in Mathematical Physics (postgraduate studies)
Taras Shevchenko National University of Kyiv1991 – 1996
Faculty of Physics, specialty: Theoretical Nuclear Physics
LANGUAGES
English — B2 (Upper-Intermediate)
RESEARCH INTERESTS
Oscillatory neural networks (Kuramoto / AKOrN) and their links to modern deep-learning models; nonlinear dynamics; applied mathematics (differential equations, Lie group theory).
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