Question 1

Which of these statements is/are true?

Answer:

• You can index multiple array fields in a single document with a single compound index - False 
  Multikey indexes allow us to index on array fields, but they do not support indexes on multiple array fields on single documents.
• Covered queries can sometimes still require some of your documents to be examined - False
  A query is covered if and only if it can be satisfied using the keys of the index.
• Write concern has no impact on write latency - False
  Different write concerns can certainly impact your write latency. Write concerns that only need acknowledgment from a primary are generally faster than ones that need acknowledgment from a majority of replica set members.
• Creating an ascending index on a monotonically increasing value creates index keys on the right-hand side of the index tree - True
• A collection scan has a logarithmic search time - False
  No, collection scans have a linear search time.