HipLocal's requirements for global expansion, scalability, and compliance with regulations like GDPR make Cloud Spanner the most suitable choice. Cloud Spanner offers a globally distributed, strongly consistent relational database service that can seamlessly scale across regions, ensuring a consistent user experience and supporting high concurrency. It also reduces infrastructure management time and cost, aligning with HipLocal's business requirements. The other options do not fully meet these needs: Cloud Datastore is a NoSQL database which may not fit their existing relational model, Cloud Memorystore is a cache service not suitable for persistent state storage, and separate Cloud SQL clusters for each region could lead to data inconsistency and increased management complexity.