Mid/Senior Backend Developer - Retail Media Platforms (NestJS, NodeJS, and TypeScript) (B2B)

Responsibilities

As a Mid or Senior Backend Developer, you will join one of our engineering teams working on the technology platforms that enable OBI’s retail media and First Media capabilities across digital and physical channels. You will contribute to building scalable, data driven backend systems that allow brands to activate media, distribute content, and measure performance along the entire customer journey, from inspiration and planning through to purchase and engagement.

You will work on backend services that power headless ad serving, campaign delivery, content distribution, targeting, analytics, and reporting across OBI’s owned channels. These platforms operate at scale, support multi-tenant publisher use cases, and require high reliability and performance for internal product teams and external advertising partners.

You will work closely with product, DevOps, and data teams to design, build, and operate backend services that enable real time activation, data processing, and reporting, while ensuring availability, performance, and operational stability across the media technology stack.

Key Responsibilities:

• Design, build, and maintain backend services using NestJS, NodeJS, and TypeScript.

• Architect and scale headless advertising platforms and backend services for online marketing and retail media use cases.

• Contribute to the architecture and scaling of distributed, cloud native systems running on AWS and Kubernetes.

• Collaborate closely with DevOps teams to manage infrastructure using Terraform, Helm, and GitLab CI/CD.

• Implement and operate event driven and streaming solutions using Kafka.

• Ensure high availability, performance, and reliability through strong observability practices.

• Use Grafana, Loki, and Thanos to monitor systems, analyze logs, and support incident response.

• Actively participate in code reviews, architectural discussions, and technical decision making.

• Contribute to continuous improvement initiatives across performance, scalability, security, and operational excellence.

• Support and evolve large scale publisher platforms, multi-tenant content management systems, and advertising platforms.

Qualifications

• Successfully completed university degree in (business) computer science, (business) mathematics, physics or similar.

• Proven experience as a Mid-level or Senior Backend Developer in production environments.

• Deep expertise in NestJS, NodeJS, and TypeScript.

• Hands on experience with AWS and cloud native architectures.

• Solid knowledge of Kubernetes, containerized workloads, and distributed systems.

• Practical experience with Terraform, Helm, and GitLab CI/CD.

• Experience working with Kafka or comparable messaging and streaming platforms.

• Strong background in monitoring and alerting, including metrics, logging, and incident response.

• Hands on experience with Grafana, specifically Loki and Thanos.

• Experience working in large scale organizations with complex stakeholder and system landscapes.

• Proven background in online marketing platforms, retail media, headless ad servers, or ad tech ecosystems.

• Experience operating or integrating large scale publisher platforms and content management systems.

• Strong understanding of multi-tenant architectures and information architectures at scale.

• Strong collaboration skills and the ability to work across engineering, product, and operations.

• Fluency in English and Polish.

• Openness to hybrid work in our Katowice office and collaboration across international teams.

Develop yourself and the digital future – at Reply!

Reply is made up of a network of highly specialised companies, which support leading industrial groups in defining and developing business models to optimise and integrate processes, applications and devices, using new technology and communication paradigms, such as Artificial Intelligence; Big Data; Cloud Computing; Digital Communication; Internet of Things; Mobile and Social Networking.