This document is entitled “D4.1 – Infrastructure & Services Definition” and represents the first deliverable of Work Package 4 of the EO4EU project. This document focuses on the following outcomes: • List the services and components of the EO4EU platform and their respective purpose. • Provide an initial snapshot of the infrastructure requirements for the platform’s components & services. • Provide an overview of the available infrastructure to be utilized for hosting the EO4EU platform. • Explain the methodology on how the multi-cloud infrastructure can be achieved encompassing all the available infrastructure resources. • State on which infrastructure each component or group (Tiers) of components/services will be hosted and the reasoning behind that choice. • Provide a summarized version of infrastructure requirements taking into account the overall needs of all the components collectively. The 3 main infrastructures available are the WEkEO, CINECA Cloud and CINECA High Performance Computer (HPC). WEkEO infrastructure will host the Platform Controller, CINECA Cloud will host all other components utilizing a Kubernetes Multi-Cluster and the Machine Learning/Inference Server service will be hosted by CINECA HPC, allowing for the best possible performance for ML model trainings. The specific computational, memory, storage and Graphics Processing Unit capabilities are summaries at the end of section 4.