Данил

Danil Kostin
Location: Kiev, Ukraine Phone: [open contact info](look above in the "contact info" section) Email: [open contact info](look above in the "contact info" section)
GitHub: https://github.com/codememory1 Telegram: @danilcm
LinkedIn: [open contact info](look above in the "contact info" section)

About me
Senior PHP/Symfony Backend Engineer with 5+ years of commercial experience building backend and full-stack
applications, including high-load fintech systems. Experienced in designing scalable architectures, developing complex
financial workflows, and collaborating with cross-functional teams to deliver reliable software. Strong focus on
Domain-Driven Design (DDD), CQRS, and long-term maintainability.

Skills
PHP Symfony PostgreSQL Doctrine ORM
RabbitMQ Redis REST APIs Docker
High-Load Systems DDD CQRS Outbox Pattern
Saga Event-Driven Architecture Microservices Vue.js
Nuxt.js TypeScript Laravel Go

Work experience
05/2023 – 04/2026 Senior Backend Engineer (Full-Stack)
Tbilisi, Georgia Confidential Fintech Company

• Designed and implemented batch processing for blockchain transactions, grouping
compatible orders into shared transactions and reducing network fees by more than 10x.

• Redesigned the fund reservation workflow, reducing asset lock time during order creation
from approximately 1 hour to 2 minutes.

• Developed an adaptive network fee calculation algorithm based on current network
conditions, significantly reducing stuck transactions during periods of high network
congestion.

• Designed and implemented a cryptocurrency deposit infrastructure with per-user address
generation, blockchain monitoring, and automated balance crediting.

• Developed an internal reconciliation system that compared partner balances, orders, and
blockchain transactions to automatically detect discrepancies.

• Developed a support ticketing system with department-based routing, real-time chat using
Pusher, file uploads to Amazon S3, complete order context, and support actions such as
manual confirmation and cancellation.

• Developed and integrated an AI chat agent using the OpenAI API, enabling users to initiate
supported account operations through natural-language conversations.

Tech stack: PHP 8.3, Symfony 7.1, Doctrine ORM, PostgreSQL, RabbitMQ, Symfony Messenger,
PHPUnit, Redis, Docker, Nginx, Vue.js, Nuxt.js, TypeScript, AWS SDK, Sentry, Playwright

02/2023 – 04/2023 Middle Full-Stack Developer
Chisinau, Moldova BPay SRL

• Improved report parameter handling by adding parameter schemas, validation, and
support for dynamic values.

• Implemented asynchronous report generation using Symfony Messenger and RabbitMQ,
allowing reports to be processed in the background with execution status tracking.

Work experience
• Developed scheduled email reporting with configurable templates, parameters, execution
intervals, and recipient lists.

• Developed support for PHP scripts as a data source, allowing administrators to configure
scripts, define their input parameters, organize them into folders, and use their results in
reports.

Tech stack: PHP 7.4, Symfony 5.3, Doctrine ORM, MySQL 8, RabbitMQ, Symfony Messenger,
Twig, Docker, Amazon S3
01/2021 – 01/2023 Middle Backend Developer
Remote Code Pilots

• Developed a subscription and paid-access module with pricing plans, access permissions,
free trial periods, usage tracking, and payment API integration.

• Implemented administrator activity auditing with a complete history of operations and
data changes.

• Developed an image upload and processing workflow with crop support and storage in
Amazon S3.

• Implemented user authentication through Google and Yandex using OAuth 2.0.

• Developed an automated notification system that allowed users to follow auction lots and
receive email updates.

Tech stack: PHP 8, Symfony 5.4, Doctrine ORM, CodeIgniter, DDD, PostgreSQL, WebSockets,
REST APIs, Amazon S3, OAuth 2.0, Docker

Education
09/2018 – 06/2022 Automotive Engineering | Technical Diploma
Mariupol, Ukraine Mariupol Construction Technical College