Machine Learning Engineer

Overview

Wallapop is a Barcelona based scale-up driven by the purpose to empower people to embrace a more conscious and human way of consumption. We believe in a world where collaborative economy is mainstream. This is what drives us. 💫

Wallapop operates in Spain, Italy and Portugal, offering a catalogue of several hundreds of millions of products and services. Powered by technical innovation and continuous improvement, we bring together the scale & trust of classifieds with the marketplace’s convenience & reach. 🌱 Our mission is to enable a connected trade ecosystem, making 2nd-hand the norm through smart use of technology.

The Challenge 🧩

Wallapop generates billions of data points daily. With a mature data infrastructure already in place, our Data Science and Machine Learning area is gaining significant momentum. As we scale, we face the exciting challenge of taking our ML Platform to the next level to support complex solutions in Personalization, Search, Trust & Safety, and Logistics. As a Senior ML Engineer, you will lead the evolution of our ML Platform and MLOps practice. You will partner with Data Scientists, Data Engineers, and DevOps to shape a vision that balances innovation with reliability, ensuring our models scale efficiently to serve millions of users.

What You Will Do 👇

Iterate and maintain Wallapop’s ML Platform, identifying opportunities to improve speed, reliability, and maintainability. You will define the long-term vision and roadmap for MLOps.
Work hand-in-hand with Data Scientists to support their efforts, ensuring they have the tooling to develop, deploy, and monitor scalable models efficiently.
Define and promote engineering best practices (coding standards, testing, CI/CD) within the ML domain.
Partner with Data Engineering and DevOps to align ML development with company-wide infrastructure and data governance standards.
Investigate and integrate new frameworks and tools (e.g., for LLMs or real-time inference) to keep our stack modern and effective.

Company:

Wallapop

Qualifications:

What We’re Looking For 🔎

Proven experience building and owning production-ready ML platforms and pipelines. You understand the full lifecycle from experimentation to monitoring.
Deep understanding of AWS components (SageMaker, Lambda, S3) and container orchestration with Kubernetes.
Strong software engineering background with proficiency in Python, Git, and CI/CD workflows. You write robust, testable code.
Experience with real-time ML architectures, leveraging tools like Kafka for low-latency ingestion and inference.
Hands-on experience with vector databases or semantic search infrastructure (e.g., OpenSearch, Vertex AI), including indexing and retrieval tuning.
Familiarity with the broader ML toolkit, such as orchestration/tracking tools (Flyte, MLFlow, Feast) and standard libraries (Pandas, Scikit-learn, TensorFlow/PyTorch).
Professional proficiency in English and Spanish, with the ability to explain complex technical concepts to diverse stakeholders.

What Would Be A Plus 🚀

Hands-on experience working with LLMs, RAG architectures, and libraries like LangChain or LlamaIndex.
Familiarity with Big Data technologies like Spark or Beam.
Experience with Data Engineering tools such as Airflow, dbt, or Datahub.
Experience with other cloud platforms like GCP or Azure in addition to AWS.

Tagged as: Big Data, Classification, Industry, Machine Learning, Spain