C100DEV MongoDB Overview and Document Model 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.

• ✗

  Create a hashed index on the 'timestamp' field

  Why it's wrong here

  Hashed indexes support equality queries by hashing the field value, but they do not support range queries because the hash destroys the ordering of values. Since the application needs to query a range (a specific day), a hashed index would not be usable for that query pattern.

• ✗

  Create a compound index on {timestamp: 1, _id: 1}

  Why it's wrong here

  A compound index on timestamp and _id can support queries on timestamp alone, but the additional _id field is unnecessary if queries only filter by timestamp. It would consume more space and slightly slow writes without providing extra benefit for the stated queries. A single-field index is sufficient and more efficient.

• ✗

  Create a text index on the 'timestamp' field

  Why it's wrong here

  Text indexes are designed for string content and support text search with stemming and tokenization. They cannot efficiently handle range queries on date values. Using a text index on a date field would not support the day-range query and would be inappropriate for the data type.

• ✓

  Create a single-field index on the 'timestamp' field

  Why this is correct

  A single-field index on 'timestamp' allows MongoDB to efficiently locate documents within a date range, such as a specific day. Since the query filters on timestamp, this index directly supports the query pattern, reducing the number of documents scanned. It is the most straightforward and effective solution for range queries on a single field.