Senior Backend

Holycode is seeking an experienced Senior Backend Developer to join our Classic Trader engineering team and drive our technical evolution forward.

About Classic Trader

Classic Trader is Europe's largest online marketplace for classic vehicles, serving collectors and enthusiasts worldwide. Our platform features over 14,000 vehicle listings, attracts 6+ million monthly page views, and is complemented by our print magazine published six times annually.

About the Role

We're at an exciting inflection point—modernizing our backend infrastructure while scaling our platform. You'll play a pivotal role in leading our migration to contemporary technologies, reducing technical debt, and architecting solutions that serve millions of users. As a senior member of the team, you'll provide technical direction, mentor other developers, and make key architectural decisions.

What You'll Work On

• Lead the migration of our backend stack from legacy systems (PHP 7.1, Symfony 2.8) to modern architecture
• Drive technical decisions and define architectural standards for the team
• Reduce technical debt and implement long-term architectural improvements
• Optimize platform performance: improve API response times, database query efficiency, and overall system throughput
• Profile and eliminate performance bottlenecks across the application stack
• Design and build scalable APIs for our marketplace and CT Inspections product
• Implement caching strategies and optimize resource utilization
• Establish and improve testing practices (unit, integration, and end-to-end tests)
• Streamline development workflows and improve team efficiency
• Mentor and guide other developers through code reviews and knowledge sharing
• Coordinate technical work and ensure code quality standards across the codebase
• Scale infrastructure to handle increasing traffic and new product lines

What We're Looking For

Required:

• 6+ years of backend development experience with web applications and APIs
• Strong expertise in PHP and Symfony framework (experience with both legacy and modern versions highly valued)
• Proven track record in technical migrations and modernization projects
• Demonstrated experience in performance optimization, profiling, and reducing API response times
• Deep understanding of software architecture principles (SOLID, design patterns, clean code)
• Production experience with relational and NoSQL databases, including query optimization
• Experience with AWS, DevOps practices, and cloud infrastructure
• Strong communication skills and ability to mentor other developers
• Experience making architectural decisions and driving technical direction
• Pragmatic approach to leveraging AI tools to enhance productivity and code quality
• Focus on efficiency, automation, and streamlining development processes

Nice to Have:

• Experience setting up and maintaining comprehensive test suites (PHPUnit, integration tests, etc.)
• Familiarity with modern frontend frameworks (React, Vue, Angular, Svelte)
• Experience with ElasticSearch, Redis, or similar technologies
• Background in e-commerce or marketplace platforms
• Experience with APM tools and performance monitoring solutions
• Knowledge of CI/CD pipelines and automated testing workflows

Our Technology Stack

Current (in migration):

• Backend: PHP 7.1, Symfony 2.8, MySQL, Redis, ElasticSearch
• Frontend: Astro, Preact, Tailwind

Target: Modern PHP 8.x with Symfony 7+ (tbd) and cloud-native architecture

Why Join Us?

This is a rare opportunity to lead meaningful technical transformation at a well-established platform while working with a team that values craftsmanship, continuous improvement, and work-life balance. If you're passionate about clean architecture, enjoy solving complex migration challenges and performance optimization problems, leverage modern tools to work efficiently, and want to leave your mark on a product that serves a vibrant community, we'd love to hear from you.

Why you'll love working here:

• Private health insurance
• Flexible work model – hybrid or full remote
• Equipment of your choice (laptop, monitor, accessories)
• High-growth company with innovative products
• Supportive, international team
• Budget for professional development (courses, books, conferences)
• English and German language lessons during working hours
• Nice office in Belgrade with a stocked kitchen and game area
• Opportunity to learn, grow, and make a real impact

If you are looking for an environment where you can grow professionally, learn from the best in the field, balance work and life habits and have a pleasant and enthusiastic environment, please submit your CV in English.

---