Full-Stack Engineer

About Seedtag

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 700+ 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 a Full-Stack Engineer in the AdServing team, you’ll help shape two of Seedtag’s most critical tools: Our SDK, the agent embedded in 200M+ devices daily, responsible for rendering ads in real time. Studio Pro, the creative tool used by designers to build contextual ads across multiple formats and devices. You’ll be working with modern, typed front-end languages (Rescript and React), building performant interfaces and reliable APIs, all while collaborating with design and backend teams to make sure everything just works. We’re looking for someone who enjoys solving hard problems, cares about maintainable code, and is ready to make key architectural decisions as the product evolves.

Your Day-to-day Will Include

• Designing and implementing client-side features for the SDK and Studio Pro.
• Developing scalable backend APIs to support dynamic creative logic and data syncing.
• Collaborating with designers, backend engineers, and product stakeholders to align on needs and priorities.
• Working across the stack, from micro frontends to backend services.
• Applying and advocating for clean code, testing, performance, and maintainability.
• Taking ownership of key features and mentoring others as the team grows.

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

We operate at large scale, supporting up to 120k requests per second, with ML models responding in under 10 milliseconds and processing 20 TB of data daily. Our Stack Includes: Languages: Python, Go, TypeScript, Scala; Cloud & Infrastructure: Kubernetes, GCP, AWS; Streaming: Kafka, Kinesis; Data: Datalakes, GCS, Redis, Druid, MongoDB; Architecture: 100+ microservices, DevOps-driven, continuous deployment.

What You’ll Need to Succeed

• You’re a full-stack engineer with 5+ years of experience. Comfortable jumping between front-end and back-end, and have built and maintained production-level apps using typed languages.
• You’ve worked on high-performance frontend applications and care about performance, UX, and stability across browsers and devices.
• You’ve contributed to developer-facing tools, SDKs, or design systems, and enjoy solving complex problems at the intersection of UX and code.
• You write clean, maintainable code and know how to apply software engineering principles to keep things simple and robust.
• You’re a strategic thinker, able to connect product needs with technical decisions and architecture.
• You enjoy a good challenge and love finding elegant solutions to complex problems.
• You’re always learning and staying up to date with new tech, frameworks, and practices.
• You’re a strong communicator who thrives in collaborative environments.
• You’re adaptable and used to working in fast-paced environments where priorities shift quickly.

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, offsites, 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.

Key skills/competency

• Full-Stack Engineer
• ReScript
• React
• API Development
• Microservices Architecture
• Cloud Computing (GCP, AWS)
• Kubernetes
• Data Engineering
• AI/ML Integration
• Software Development Principles