Senior Backend Engineer (AdTech)

Location: Warsaw / pl / Remote

• Take end-to-end ownership of the Vast Gateway service
• Maintain, develop, and extend platform functionality
• Design and implement scalable Back-end solutions for high-load environments
• Support onboarding of new clients, including integrations, monitoring setup, troubleshooting, and optimization
• Build custom features and integrations based on Customer requirements
• Monitor system performance and proactively identify optimization opportunities
• Ensure service reliability, availability, and low-latency performance
• Participate in release planning, deployments, and production support activities
• Improve observability through monitoring, alerting, and operational tooling
• Collaborate with Product and engineering stakeholders to evolve platform architecture

Requirements

• 5+ years of commercial Back-end development experience
• Strong expertise in server-side JavaScript or other Back-end technologies
• Commercial experience in AdTech environments
• Proven experience supporting production systems in high-load environments
• Strong understanding of debugging, monitoring, hotfixing, and zero-downtime deployments
• Solid knowledge of HTTP protocols, web fundamentals, HTML, and tracking pixels
• Experience building scalable and highly available distributed systems
• Strong analytical and problem-solving skills
• Ability to independently own services and drive technical improvements
• Upper-Intermediate English level or higher
• Strong communication and collaboration skills in distributed teams

Will be a plus

• Experience with VAST protocol
• Hands-on experience with Cloudflare Workers
• Experience with VPAID creatives
• Background in video advertising technologies
• Experience with high-load distributed systems
• Performance optimization expertise
• Experience with edge-computing architectures

Personal Profile

• Analytical and data-driven mindset
• Strong ownership mentality
• Proactive approach to identifying issues and improvement opportunities
• Comfortable working autonomously in a high-responsibility role
• Detail-oriented with a focus on reliability and quality
• Strong troubleshooting and decision-making skills

Our Customer is a cybersecurity-focused company delivering solutions that help protect organizations, users, and digital ecosystems from online threats. The company develops products for high-traffic environments where reliability, scalability, and security are essential. Their solutions help detect vulnerabilities, ensure secure digital experiences, and protect users from malicious activity across multiple industries.

Project

You will join the team working on Vast Gateway, a high-throughput edge proxy built on Cloudflare Workers and responsible for handling tens of millions of requests per day within the video advertising delivery flow.

The platform retrieves and processes VAST responses, applies modifications including malicious ad protection logic for VPAID creatives, and consolidates multiple VAST documents into a single XML response for video players. Since all advertising traffic flows through the gateway, the system is designed with a strong focus on low latency, high availability, scalability, and operational stability.