The database services covered in Week 5 were each built to solve a different problem. RDS runs traditional relational DBs without the management burden; Aurora overcomes the limits of relational DBs through storage redesign; DynamoDB serves hundreds of millions of items in milliseconds without a schema; ElastiCache delivers repeated reads at memory speed. Today is the day to firmly organize how these services are tested on the exam.
Most exam questions come in the form "which would you choose in this scenario?" The key is finding the reason one option — while several may look technically possible — is better than the rest