Final Answer:
Cloud Spanner is the database service that provides transactional consistency at a global scale, leveraging a distributed architecture with synchronous replication for ACID-compliant transactions across regions. Thus the correct option is B. Cloud Spanner.
Step-by-step explanation:
Cloud Spanner is the database service that offers transactional consistency at a global scale. Unlike traditional databases that face challenges in providing consistency across distributed systems, Cloud Spanner utilizes a globally distributed architecture with synchronous replication, ensuring that transactions are ACID-compliant (Atomicity, Consistency, Isolation, Durability) even in a geographically distributed environment.
The unique combination of horizontal scaling and globally distributed transactions sets Cloud Spanner apart in delivering both strong consistency and global availability.
In Cloud Spanner, data is horizontally sharded across multiple nodes, and these nodes are distributed across different regions. The globally distributed architecture allows users to read and write data from any region, ensuring low-latency access and redundancy.
The underlying TrueTime API helps synchronize clocks across globally distributed servers, addressing challenges related to clock skew and ensuring consistent timestamps for transactions. This synchronization is crucial for maintaining the integrity and consistency of the database at a global scale.
Moreover, Cloud Spanner provides strong external consistency, allowing developers to execute transactions with confidence, knowing that the system will enforce consistency guarantees even in the face of network partitions or failures.
With its unique combination of features and architecture, Cloud Spanner stands out as a database service that offers transactional consistency at a global scale, making it a robust choice for applications that require both geographic distribution and strong consistency across their data.
Thus the correct option is B. Cloud Spanner.