Question 1

In designing a database schema for a MongoDB application that handles user-generated content, such as posts and comments, a data modeler is considering the most efficient way to store comments related to each post to optimize read operations, as the application experiences significantly more reads than writes. The application requires frequent retrieval of posts along with their associated comments. What pattern should the data modeler use to store comments in relation to posts, and why?

Options :

A : Reference Pattern

B : Subset Pattern

C : Bucket Pattern

D : Normalized Pattern

E : Embedded Pattern

Answer: E

Question 2

To improve the performance of queries on a logEntries collection, a MongoDB developer needs to find and analyze slow queries that have been executed. Which command should be used to identify and provide details on slow operations for analysis?

Options :

A : db.adminCommand({ "getLog": "global" })

B : db.setProfilingLevel(2, { "slowms": 100 })

C : db.logEntries.find({ "slowQuery": { $exists: true } })

D : db.logEntries.aggregate([ { $currentOp: { "slowOp": true } } ])

Answer: A

Question 3

A team is developing a logistics application using MongoDB to track shipments in real-time. Each shipment record updates frequently with GPS coordinates, and the system requires immediate access to the latest location data for efficient routing and delivery updates. The application also needs to maintain a compact record of each shipment's path without unnecessary data duplication. Which MongoDB feature or design pattern should be used to model the shipment tracking system?

Options :

A : The Bucket Pattern, grouping location updates by day for each shipment.

B : The Preallocation Pattern, by preallocating space for each shipment document to accommodate location updates.

C : The Document Versioning Pattern, where each update creates a new version of the shipment document.

D : A standard collection with an index on the lastUpdated field.

Answer: D

Question 4

In MongoDB schema design, what is a critical implication to consider when adding another piece of data into an array field, especially in the context of document size limitations and performance?

Options :

A : Arrays do not impact document size, allowing for unlimited data addition without performance concerns.

B : Adding elements to an array increases the risk of exceeding the BSON document size limit, potentially leading to failed updates.

C : Adding data to arrays significantly improves query performance by utilizing array-specific indexes.

D : Each addition to an array requires a complete document rewrite, which has no impact on performance or storage.

Answer: B

Question 5

In a MongoDB database tracking e-commerce orders, each order document includes fields for customer ID, order date, and a status that changes over time. To automatically purge orders older than two years and efficiently support queries for recent orders by customer ID, which combination of indexes would be most appropriate?

Options :

A : A compound index on customer ID and order date, and a TTL index on the status field.

B : A single-field index on the customer ID and a Time-To-Live (TTL) index on the order date.

C : A text index on the customer ID for efficient search and a TTL index on the order date.

D : A hashed index on customer ID and a TTL index on the order date.

Answer: B