You must model transactional data for an ML-based food-ordering service (user profiles, account info, orders) and optimize the schema for transactions. Which GCP product should you use?

Cloud SQL is the correct choice because it is a fully managed relational database service that supports transactional workloads (ACID properties) and is ideal for structured data like user profiles, account information, and orders. Its SQL interface is well-suited for complex queries and maintaining data integrity, which is crucial for a transactional food-ordering service. BigQuery is a data warehouse optimized for analytical queries on large datasets, not transactional processing. Cloud Bigtable is a wide-column NoSQL database designed for high-throughput, low-latency access to large amounts of data, typically for operational analytics or time-series data, not for complex transactional relationships. Cloud Datastore (now part of Firestore in Datastore mode) is a NoSQL document database suitable for semi-structured data and scalable applications, but Cloud SQL offers stronger transactional guarantees and a more traditional relational model which is often preferred for financial or order-based systems.