A company is planning to host its datastore in AWS for its 3-tier application. The following are the key requirements for the database.
- The ability for multiple schema changes
- The relational database should be durable
- Changes to the relational database should not result in downtime
Which of the following would be the best datastore option for the company?

Answer options:

A.AWS S3
B.AWS Redshift
C.AWS DynamoDB
D.AWS Aurora

Correct Answer: D
AWS Says, "In Amazon Aurora, you can use fast DDL to execute an ALTER TABLE operation in place, nearly instantaneously. The operation completes without requiring the table to be copied and without having a material impact on other DML statements. Because the operation doesn`t consume temporary storage for a table copy, it makes DDL statements practical even for large tables on small instance types.
Here’s a performance comparison—you can see that Aurora is doing a constant time operation updating the Schema Version Table. In contrast, regular MySQL grows in a near-linear fashion with table size.
Amazon Aurora is a MySQL-compatible database that combines the speed and availability of high-end commercial databases with the simplicity and cost-effectiveness of open-source databases. Amazon Aurora has a taken a common data definition language (DDL) statement that typically requires hours to complete in MySQL and made it near-instantaneous.i.e.0.15 sec for a 100BG table on r3.8xlarge instance. 
For more information, please refer to the below link-
https://aws.amazon.com/blogs/database/amazon-aurora-under-the-hood-fast-ddl/