Which of the following is WRONG for NoSQL databases? (Select TWO.)

Answer options:

A.They are not relational.
B.They need to have a well defined schema.
C.DynamoDB Transactions is NOT atomicity, consistency, isolation, and durability (ACID) compliant.
D.NoSQL databases are horizontally scalable.
E.A patient’s record in a hospital system with changing data for every visit is a good candidate to be modelled using a NoSQL database.

Answers: B, C
Option A is incorrect since NoSQL databases are not relational. They support data that are semi-structured or unstructured as compared to the structured nature of relational databases like Oracle, MySQL.
Option B is CORRECT.NoSQL databases do not support a predefined schema like a relational database does (e.g. A record of type Book will have a fixed set of attributes defining a schema like ID, Name, Description, Author). Not defining a rigid schema allows NoSQL databases the flexibility to support semi-structured & unstructured data.
Option C is CORRECT. DynamoDB transactions provide developers atomicity, consistency, isolation, and durability (ACID) across one or more tables within a single AWS account and region. The details can be found in https://aws.amazon.com/cn/blogs/aws/new-amazon-dynamodb-transactions/.
Option D is incorrect. NoSQL databases are usually run in compute node clusters with data being partitioned across these nodes. Partitioning happens automatically with an increase in database size resulting in horizontal scaling.
Option E is incorrect. A Patient’s medical record during hospital visits may be updated by multiple people e.g. Billing information, Medicines, BP, Height, Weight etc...Defining a person’s medical history in a structured format will be impractical & inefficient. Another way to look at a patient’s medical record is as a set of documents with a new document being added during every visit with additional information.
Diagram:
References:
Intro to AWS Database services
https://youtu.be/eKyS9rvbj40
 2. AWS database services documentation
https://aws.amazon.com/products/databases/