For strong consistency, which database technologies are typically used in strong consistency mode?

For strong consistency, which database technologies are typically used in strong consistency mode?

• A. PostgreSQL, MySQL, Google Spanner, or DynamoDB in strong mode.
• B. Redis in cluster mode.
• C. MongoDB without replication.
• D. An in-memory cache alone guarantees strong consistency.

Answer: (A)

Strong consistency means every read reflects the most recent write, even across distributed nodes, which is achieved by systems that enforce linearizable, ACID-style guarantees or global time-based coordination. The best choice lists PostgreSQL and MySQL, which provide robust ACID transactions and, when configured with synchronous replication, maintain the latest committed state across replicas; Google Spanner is designed for global strong consistency using TrueTime to coordinate across regions; and DynamoDB offers strongly consistent reads as an option, ensuring you see the latest data when you request it. Redis in cluster mode, while fast, does not guarantee strong consistency across shards and replicas in typical deployments. MongoDB without replication lacks the distributed redundancy that supports cross-node strong guarantees, and an in-memory cache by itself does not provide durable, cross-system strong consistency.

Strong consistency means every read reflects the most recent write, even across distributed nodes, which is achieved by systems that enforce linearizable, ACID-style guarantees or global time-based coordination. The best choice lists PostgreSQL and MySQL, which provide robust ACID transactions and, when configured with synchronous replication, maintain the latest committed state across replicas; Google Spanner is designed for global strong consistency using TrueTime to coordinate across regions; and DynamoDB offers strongly consistent reads as an option, ensuring you see the latest data when you request it.

Redis in cluster mode, while fast, does not guarantee strong consistency across shards and replicas in typical deployments. MongoDB without replication lacks the distributed redundancy that supports cross-node strong guarantees, and an in-memory cache by itself does not provide durable, cross-system strong consistency.