A. Indexes can be traversed both forward and backward.

B. Index prefixes cannot be used in query predicates to increase index utilization.

C. Index prefixes can be used in sort predicates to prevent sort in memory.

D. It's possible to have a sorted query use an index for both sorting and filtering.

A. more useful an index created on this field will be.

B. less useful an index created on this field will be.

A. A course model needs to store references to image of the course that are kept in an external location outside the database.

B. A course model needs to store a counter representing the number of times it was purchased.

C. Our app needs to retrieve a course and its ten most recent reviews.

D. Our app needs to retrieve a course and information about its instructor.

A. No

B. Yes

A. db.football_players.find( { "last_name": "Lewandowski", "details.country": { "$gt": "D" } } ).sort( { "details.country": 1 } )

B. db.football_players.find( { "last_name": { "$gte": "L" } } ).sort( { "details.club": -1 } )

C. db.football_players.find( { "last_name": "Lewandowski" } ).sort( { "details.country": 1, "details.club": 1 } )

A. Setting a node's priority to 0 ensures that a node never becomes primary.

B. Not all nodes have equal chances to become the primary node.

C. Elections can take place anytime while the primary is available.

D. Nodes with a higher priority are more likely to be selected as primary node.

A. Yes, it will only insert a document with an _id field (auto-generated).

B. Yes, it will only insert a document without any fields.

C. No, it will throw an error.

A. db.movies.find( { languages: { $size: 5 } } )

B. db.movies.find( { languages: 5 } )

C. db.movies.find( { languages: { $eq: 5 } } )

D. db.movies.find( { languages: { $gt: 5 } } )

A. Dictionary

B. String

C. ObjectId

D. Boolean

E. Array

A. Because we have less and less disk space.

B. Because we also need to update the index.