Open to opportunities

Serhii Smirnov

@serhiismirnov

Message

Senior backend developer designing scalable PHP/Symfony architectures and leading delivery teams.

Poland

Message

What I'm looking for

I’m looking for a role where I can architect and modernize high-load backend systems, apply DDD/Clean Architecture and microservices thoughtfully, and lead remote delivery with strong engineering practices and measurable performance, reliability, and scalability outcomes.

I’m a senior backend developer with 18 years of experience in web development, specializing in backend systems and the design of robust, scalable architectures. A key part of my work is architecting and delivering complex systems with strategic technical decisions that support long-term success.

I modernise legacy systems and introduce microservices architectures where appropriate to improve scalability and maintainability. I design using Domain-Driven Design with The Clean Architecture, Hexagonal/Onion Architecture concepts, and SOLID principles, and I’ve applied CQRS and Event Sourcing.

In recent roles, I’ve decoupled autonomous services from monolithic codebases, improved reliability through refactoring into Clean Architecture with DDD, and implemented event-driven integration (e.g., introducing Event-Driven Architecture using Google Pub/Sub as a message broker). I’ve also led technical work that improved performance and stability, including caching and Doctrine batch optimizations.

My hands-on expertise centers on PHP with Symfony as my primary framework, supported by deep relational database knowledge (especially MySQL) and MongoDB certifications. I enjoy pragmatic problem-solving, refactoring, API design (REST/GraphQL), and collaborating with remote teams to deliver measurable results.

Experience

Work history, roles, and key accomplishments

Current

Backend Developer

Current

CapsLock

Aug 2025 - Present (10 months)

Decoupled a monolithic codebase into autonomous services and improved synchronization using event-driven architecture with Google Pub/Sub. Refactored services using Clean/Hexagonal Architecture with DDD principles, reducing bot-detection response time by 2x and eliminating Doctrine batch memory leak issues.

Microservices Hexagonal Architecture PHP Symfony Google Pub Sub Twilio CI CD

Software Architect / Backend Developer

Yavdoma.com

Aug 2023 - Jul 2025 (1 year 11 months)

Created a competitive, scalable hotel bookings system that was 75% faster than competitors and successfully delivered the product to market. Led a remote team of five and designed DDD/Hexagonal Architecture, building Symfony REST APIs, async processing with RabbitMQ, and scaled MongoDB across five servers.

Software Architecture Hexagonal Architecture Symfony MongoDB RabbitMQ REST APIs Sentry

Senior PHP/Symfony Backend Developer

Lingoda.com

Jul 2021 - Feb 2023 (1 year 7 months)

Improved backend development efficiency and sped up site page load by nearly 20% by replacing REST APIs with GraphQL. Automated teacher class observation requests to save about 10 hours per week, and integrated B2B services and synchronization between the learning platform and the B2G product.

Symfony PHP GraphQL REST APIs Docker RabbitMQ Sentry Grafana API Integration Agile Scrum

Senior PHP/Symfony Backend Developer

Chess.com

Jul 2018 - Oct 2020 (2 years 3 months)

Developed and supported backend APIs and delivered new features in PHP/Symfony. Optimized high-loaded pages by reducing SQL queries from 130 to 15, improved response time via asynchronous processing, and refactored the codebase to enable faster feature development.

PHP Symfony MySQL Redis AWS Asynchronous API Development PHPUnit Vagrant

Senior PHP Developer

Together Networks

Aug 2017 - Jun 2018 (10 months)

Performed legacy code refactoring, project support, and code reviews while supporting team members. Reduced statistics database size and improved performance by nearly 30%, prepared the platform for IPv6, and modernized obsolete solutions with new well-documented implementations.

Symfony MySQL Docker Redis RabbitMQ Elasticsearch Code Review Performance Optimization

Senior PHP/Symfony Developer

UniSender

Nov 2016 - Aug 2017 (9 months)

Refactored a monolithic Symfony application into multiple microservices, including payments, statistics, and mass-mail sending. Scaled the web application by refactoring to microservices and using Redis for caching and session storage, while integrating RabbitMQ message queues.

Symfony PHPUnit Microservices MySQL RabbitMQ Redis Docker Code Review Session Cache Design

Team Leader Backend Developer

Gravity4 Inc.

Sep 2014 - Oct 2016 (2 years 1 month)

Led remote teams while working as a team leader and supported scaling of PHP/Symfony web applications. Scaled the application using NSQ and Redis for session storage and caching, introduced BDD with Behata, and guided collaboration through daily Scrum and Kanban practices.

Team Leadership PHP Symfony NSQ Redis MySQL Message Queues Vagrant

Freelance Backend Developer

Freelancer

Aug 2013 - Sep 2014 (1 year 1 month)

Delivered multiple projects as a freelancer, building RESTful APIs and web reporting tools for various domains. Developed Symfony/MongoDB solutions and integrated Elasticsearch and Amazon S3 for search and file storage, including projects like Swapit.es and Flyflasher.com.

PHP Symfony MongoDB RESTful APIs Elasticsearch Amazon S3 API Development Reporting Performance Optimization

PHP Developer / Backend Developer

Team International Inc.

Nov 2010 - Aug 2013 (2 years 9 months)

Developed and supported enterprise publishing web applications (Lulu) using PHP and Java components. Wrote PHPUnit tests and extended RESTful web services backed by PostgreSQL and MongoDB, including modifications to existing Java Spring/Hibernate parts.

PHP Java PostgreSQL MongoDB PHPUnit enterprise applications Code Service Integration Unit Testing