Денис

Denis Denisov
[open contact info](look above in the "contact info" section) (Telegram)
Java Backend [open contact info](look above in the "contact info" section)
Developer GitHub
Spring Boot | REST API | LinkedIn
PostgreSQL | Docker
Kiev, Ukraine

About Me Hard Skills
Java Backend Developer with experience developing
and maintaining backend systems in production
environments. Skilled in building REST APIs using Spring Java Swagger
Boot, implementing authentication and authorization
with Spring Security, and optimizing backend SQL Redis
performance.
Experienced in working within a development team,
fixing bugs, refactoring existing systems, and PostgreSQL Docker
implementing new features.
Currently seeking a Backend Developer position where Spring Git
I can continue improving my skills and contribute to
building reliable backend services. SpringBoot GitHub
Soft Skills Spring Security Gitlub
Punctuality Hibernate ( JPA, JDBC ) Maven
Teamwork Rest API JUnit
Responsibility Mockito Flyway
Learnability
Projects
Analytical skills Chat “Chat Your Way” - BackEnd developer
Link back
• Maintained and improved legacy backend codebase
Work Experience • Implemented new REST API endpoints
01.2025 - 09.2025 • Fixed bugs and refactored existing functionality
Java developer in • Implemented authentication and authorization using Spring Security
Startup chat - "Chat-Your-Way" • Integrated Redis caching to improve performance
2023-2024 • Wrote unit tests using JUnit and Mockito
Freelancer (FrontEnd Developer) Technologies: Java, Spring Boot, Spring Security, Redis, Docker, REST
API, JUnit, Mockito
2013-2022
Private entrepreneur Personal Financier — Personal Finance Management System
Link back
9 years Сommercial services
Backend application for managing personal finances, accounts, transactions, budgets and
financial goals.

Education Designed RESTful API for managing users, accounts, transactions, budgets, and
08.2022 - 04.2023/ financial goals.
02.2024 - 09.2024 Implemented JWT authentication with custom security filters and token blacklist
logout.
DAN.IT Education Added email verification and account activation using verification tokens.
FrontEnd/BackEnd Developer Implemented rate limiting (Bucket4j) and login attempt protection for improved
security.
Integrated PostgreSQL database with JPA/Hibernate and MapStruct for DTO
Kyiv National Economic mapping.
Implemented global exception handling and validation for API stability.
University
Specialist Diploma / Final-project “Linkedin” (interpretation of a well-known
Оrganization management
social network). - BackEnd developer
Link back
Languages Technologies used: Java, Spring Boot, Spring Security, Swagger, Docker, REST
English API, JUnit, Mockito
B1 (Intermediate) Developed backend functionality as part of a team of 4 developers.
• Implemented user registration and authentication
Ukrainian and Russian
• Developed friend request functionality
Native
• Implemented like system for posts
• Built REST API endpoints