C100DEV Aggregation Framework Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  $limit

  Why it's wrong here

  Using $limit alone is insufficient because it simply cuts off the result set after a specific number of documents without considering their order. If the data is not sorted first, the limit will return the first 10 documents found by the cursor, which may not be the most expensive.

• ✓

  $sort followed by $limit

  Why this is correct

  This sequence is correct. The $sort stage orders the documents based on the specified criteria, and the subsequent $limit stage constrains the output to the required count. This combination is the standard approach for implementing 'top N' style queries in MongoDB aggregation pipelines, ensuring accuracy in the results.

• ✗

  $match followed by $limit

  Why it's wrong here

  $match is used for filtering records, not for ordering them by value. Using it before $limit will only restrict the documents based on specific criteria, not by price, so the output will not contain the 'top' items unless the collection was already perfectly sorted by chance.

• ✗

  $group followed by $limit

  Why it's wrong here

  $group aggregates documents into buckets. If you use it before $limit, you are limiting the number of groups, not individual items. This approach is useful for pagination of grouped results but fails to satisfy the requirement of finding the top 10 individual expensive items across the dataset.