AWS DevOps Engineer Professional Practice Test

What consistency types are supported by Global Secondary Indexes on DynamoDB?

1. Strong and Eventual Consistency

2. Only Eventual Consistency

3. Both Eventually Consistent and Strongly Consistent

4. Only Strong Consistency

The correct answer is: Only Eventual Consistency

Global Secondary Indexes (GSIs) in DynamoDB provide only eventual consistency when you retrieve data from them. This means that when you read from a GSI after a write operation, there may be a short period during which the data might not reflect the latest write, as it may still be propagating through the system. Eventual consistency allows for high availability and performance, as it does not require the database to synchronize immediately across all nodes. Instead, it ensures that, eventually, all copies of the data will converge to the most recent version. This model is particularly suitable for applications that can tolerate some lag in data retrieval and still require fast read access. On the other hand, strong consistency is not supported for GSIs. Strongly consistent reads ensure that a read operation will always return the most recent write, which can introduce more latency and affect throughput. DynamoDB supports strong consistency for the base table, but GSIs as a feature do not align with the requirements for strong consistency, which is why GSI reads are limited to eventual consistency.