Denis Varennikov
Backend Developer
Skilled Backend Developer with 5+ years of experience in building scalable backend systems. Proficient in Node.js , PHP ,
Ruby on Rails , Go , Python , C#, Java and Rust , focusing on API design , cloud infrastructure , and
databaseoptimization . Experienced in both remote and hybrid environments for international companies, delivering
high-qualitysolutions in agile teams. Passionate about optimizing system performance and ensuring reliability.
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Kyiv, Ukraine
WORK EXPERIENCE
SKILLS
Backend Developer
CentrySoft
01/2022 - 08/2025,
github.com/touridev
Białystok, Podlaskie, Poland
Ruby
Python
Go
Rust
Ruby on Rails
C#
C++
ASP.NET
Java
SpringBoot
Achievements/Tasks
Led backend development for a highly available e-commerceplatform
using Ruby on Rails and Go , which now handles over 500,000 users
daily.
Developed a real-time notification system using Redis and RabbitMQ ,
reducing message delivery latency by 35% .
Optimized GraphQL and RESTful APIs for speed and
efficiency,improving response times for key endpoints by 50% .
Designed and implemented CI/CD pipelines using GitLab CI and
Jenkins , reducing deployment time by 60% and ensuring
seamlessfeature rollouts.
TypeScript
Redis
MySQL
SQLite
Jenkins
GitLab
Angular
Node.js
CI/CD
PostgreSQL
Azure
Git
MySQL
MongoDB
Docker
Github
Kubernetes
PHP
Redis
React
Docker
AWS
Regularly traveled to the headquarters (in Europe) for sprint
planningand key milestone meetings.
Collaborated with cross-functional teams located in
multiplecountries, managing the project through Slack, Jira and
Zoom .
Open-Source E-Commerce Platform (01/2022 - Present)
Backend Engineer
Avatar Engines
06/2017 - 12/2021,
Mannheim, Baden-Württemberg,
Germany
Achievements/Tasks
Developed microservices in Go for a data processing pipeline
,handling over 10 TB of data per day. This improved
processingefficiency by 40% .
Integrated AWS Lambda for serverless data processing,
optimizingresource usage and reducing server costs by 20% .
Enhanced database performance, reducing retrieval time for key
databy 45% through advanced PostgreSQL optimizations.
Worked within an international, fully remote team, using Trello ,
GitHub , and Zoom to coordinate and deliver sprints across
multipletime zones.
Junior Backend Developer
Berezha Security Group
03/2015 - 05/2017,
PERSONAL PROJECTS
Spearheaded the backend development of a Ruby on Rails ecommerceplatform that handles over 500,000 users daily, optimizing both
performanceand scalability with Go and Redis .
Integrated real-time notifications and payment processing,
increasingcustomer satisfaction by 30% .
Technologies: Ruby on Rails, Go, MongoDB, AWS
Task Management Tool (07/2019 - 12/2021)
Designed a project management application to help teams assign tasks, set
deadlines, and track progress.
Improved team productivity and reduced missed deadlines by 35% with
automated notifications and dashboards.
Technologies: Angular, Django, PostgreSQL, Docker
E-Commerce Platform (09/2016 - 04/2018)
Developed a multi-vendor e-commerce platform with inventory management,
user authentication, and order tracking.
Successfully launched the platform supporting 50+ vendors and 5,000+ users,
increasing client revenue by 30%.
Technologies: Vue.js, Express.js, MongoDB
Kyiv, Ukraine
Achievements/Tasks
Built backend services using C# and ASP.NET for internal
tools,automating manual processes and saving the company 15%
inoperational costs.
Contributed to the migration of legacy systems to a
microservicesarchitecture , improving system uptime by 40%.
EDUCATION
Bachelor of Science in Computer Science
Taras Shevchenko National University of Kyiv
Optimized SQL queries, improving data retrieval efficiency by 20% .
Split time between working remotely and collaborating on-site with
ahybrid development team using GitHub , Jira , and Slack for
communication and task tracking.
LANGUAGES
English
Ukrainian
