This deliverable, D8.1, is part of Work Package 8 (WP8) of the HealthData@EU Pilot, a project that concluded on December 31, 2024. The HealthData@EU Pilot tested the implementation of the European Health Data Space (EHDS) infrastructure for the secondary use of health data, supporting research, innovation, policymaking, and regulatory activities. Objective D8.1 provides recommendations on standards for data interoperability, querying, and exchange based on observations from the five use cases of the pilot. The deliverable assesses the feasibility and challenges of cross-border data sharing, identifying key interoperability checkpoints and gaps in existing frameworks. Approach The analysis is structured around the HealthData@EU Data Life Cycle, as defined in the TEHDAS Joint Action, and includes: Theoretical analysis: Reviewing expected interoperability measures based on existing standards. Practical assessment: Documenting the actual data access, processing, and exchange mechanisms applied in the five use cases. Comparative evaluation: Identifying gaps between theoretical models and real-world implementation, with reference to the EHDS Regulation. Key Findings Variability in national data access frameworks, leading to interoperability challenges. Differences in metadata standards, affecting harmonization across countries. Technical and semantic interoperability issues, requiring further standardization efforts. Lessons learned from real-world implementation, informing recommendations for future EHDS infrastructure development.