Senior Software Engineer

We’re looking for a Senior Software Engineer to join our tech team and help build the future of neuro-contextual advertising at global scale.

Who We Are

At Seedtag, our mission is to transform advertising by proving that effectiveness and user privacy can truly coexist.

As the leading Neuro-Contextual Advertising Company, we combine Artificial Intelligence, Natural Language Processing, Computer Vision, and neuroscience to understand not only what content is about, but how it makes people feel and what they intend to do next.

Our proprietary AI, Liz, enables brands to connect with audiences across the open web and Connected TV without cookies or user tracking. Founded in 2014 by two ex-Googlers, Seedtag has grown to 500+ Seedtaggers in 17 countries, backed by €250M in funding, and operates today as a global ad-tech leader.

If you enjoy solving complex engineering challenges and building AI-driven systems at scale, you’ll feel right at home here.

Your Challenge

As our Senior Software Engineer, you will join our five-person Contextualization Platform team, building the technology that understands content across the open web, Connected TV (CTV), and in-app environments. You'll develop high-performance backend systems and turn AI innovations into production solutions that power contextual advertising at scale.

• Backend Development: Design, build, and maintain high-throughput, low-latency services using Golang, supporting an RTB ecosystem handling over 500K queries per second.
• AI & ML Integration: Transform Data Science experiments, LLM capabilities, and AI-driven ideas into reliable production systems.
• Scalable Architecture: Develop APIs, services, and data pipelines that process large volumes of contextual data efficiently.
• Innovation & Experimentation: Prototype, test, and iterate on new approaches to contextual understanding across OpenWeb, CTV, and in-app environments.
• Platform Evolution: Contribute to architectural decisions and continuously improve system performance, reliability, and scalability.
• Cross-Functional Collaboration: Work closely with Data Scientists, AI teams, and Product Managers to deliver solutions with measurable business impact.
• Engineering Excellence: Write clean, maintainable code while balancing quality, speed, and evolving business priorities.

Our Core Values

Outcome over Output

We measure success by impact and value, not by volume of features or lines of code.

Failure Is Allowed, Learning Is a Must

Experimentation is key to innovation. We test early, iterate often, and learn fast.

We Are All Scouts

We take ownership and leave things better than we found them.

We Are Data-Driven

Data informs our decisions and helps us continuously improve our systems and results.

Tech Stack

You'll work with technologies supporting Seedtag's scalable backend systems and AI-powered capabilities.

Our Stack Includes

• Core Language: Go / Golang.
• Additional Languages: Python, Node.js, TypeScript.
• Architecture: Distributed systems, microservices, high-throughput and low-latency services, APIs.
• AI & Machine Learning: LLM APIs, embeddings, RAG, ML model integration.
• Infrastructure & Observability: Cloud infrastructure, monitoring, Infrastructure as Code (e.g. Terraform).
• Domain: OpenWeb, CTV, in-app contextualisation, RTB.

What You’ll Need To Succeed

• Strong hands-on Golang experience, building and maintaining backend services in production.
• Solid understanding of distributed systems, particularly high-throughput or low-latency architectures.
• Hands-on experience with LLM APIs, embeddings, or RAG, alongside a strong interest in AI technologies.
• Experience with cloud infrastructure, observability, and production system monitoring.
• Familiarity with Infrastructure as Code principles and tools.
• Strong problem-solving skills and a pragmatic approach to delivering reliable, maintainable software.
• Ability to work autonomously, adapt to changing priorities, and collaborate effectively with technical and non-technical stakeholders.

It Would Be a Plus If You

• Have experience with Python, Node.js, or TypeScript.
• Have worked in AdTech, particularly with RTB, OpenRTB, or CTV.
• Have experience processing large-scale data or building real-time advertising systems.

Why Join Seedtag?

• A key moment of growth with real ownership and global impact.
• Flexible work model with 100% remote or hybrid options. (Remote contracts available in Spain, Italy, UK, Belgium, Netherlands, France, and Germany.)
• Continuous learning through a learning platform and optional language classes.
• A supportive, trust-based culture that values well-being.
• Team activities and opportunities to connect beyond work.

Additional Perks

• Home office setup budget up to €1,000
• Paid trips to our HQ in Madrid
• MacBook Pro M3

Ready to Join the Seedtag Adventure?

At Seedtag, we create an environment where everyone can thrive. If you need accommodations during the hiring process, let us know and we’ll ensure a positive experience.

Send us your CV and let’s build the future of neuro-contextual advertising together.