Answer: Cloud Spanner

The best choice for such a project is **Cloud Spanner** due to its unique combination of features: - **Automatic scaling**: Adjusts resources dynamically to meet workload demands, optimizing performance and cost. - **Transactional consistency**: Offers ACID (Atomicity, Consistency, Isolation, Durability) properties, ensuring reliable transactions. - **Scalability**: Capable of handling up to petabytes of data and thousands of queries per second, ideal for large-scale applications. - **SQL querying**: Utilizes a SQL-like language, facilitating easy integration and development. While alternatives like Cloud SQL and Cloud Datastore provide some of these capabilities, Cloud Spanner stands out for projects with these specific, demanding requirements.

Author: LeetQuiz Editorial Team