MongoDB Updated C100DBA Exam Questions and Answers by erica

The query first applies .sort({ price: -1 }). In MongoDB, -1 specifies descending order, so the result stream is ordered from the highest price to the lowest: Laptop at 1500, Smartphone at 800, Tablet at 600, Monitor at 300, and Headphones at 200. The subsequent .limit(2) restricts the cursor to the first two documents in that sorted sequence. Therefore, only Laptop and Smartphone are returned. Option B identifies the two lowest-priced products rather than the highest. Option C reflects the sort but ignores the limit(2) stage. Option D shows the two lowest products in ascending order and therefore contradicts both the requested sort direction and the limit semantics. For a large collection, a single-field index on price could support this sort efficiently because MongoDB can traverse an index in either direction; an ascending index can be scanned backward to satisfy a descending sort and vice versa. The logical query result, however, is independent of whether such an index exists. Option A is the correct output.

Study Guide reference/topic:MongoDB Architecture and Core Operations - cursor sorting, limiting result sets, and query result ordering.

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MongoDB supports a clean server shutdown through the shutdown administrative command and through the mongosh helper db.shutdownServer(). Option A uses db.adminCommand({ shutdown: 1 }), which executes the shutdown command against the admin database and requests an orderly termination of the server process. Option D explicitly switches to the admin database and calls db.shutdownServer(), the documented shell helper that wraps the same administrative behavior. Option B uses killOp, which terminates a specific database operation identified by an operation ID; port 27017 is not an operation ID and killing an operation is not equivalent to shutting down mongod. Option C uses killAllSessions, which ends logical sessions but leaves the server process running. A controlled shutdown is preferred over abruptly terminating the process because MongoDB can close resources and complete its shutdown procedures cleanly. In replica-set deployments, administrators should also consider whether the member is primary and whether a planned step-down is appropriate before maintenance. Among the commands shown, A and D are the two valid mongosh-based shutdown mechanisms.

Study Guide reference/topic:MongoDB Architecture and Core Operations - clean server shutdown, admin commands, and db.shutdownServer().

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The operation must update every matching document and use the $inc update operator with correct syntax. updateMany() applies the update to all documents matching { color: " green " }. The $inc operator must be the top-level update operator and receive a field-to-amount mapping, so the valid update document is { $inc: { price: 5 } }. Option C satisfies both requirements. The sweater price increases from 20 to 25, and the hat price increases from 12 to 17. Option B uses a syntactically correct $inc expression, but the legacy update() call shown does not explicitly request a multi-document update, so it does not meet the stated requirement to modify all green products. Options A and D place $inc beneath the price field instead of placing $inc at the update-operator level, which is not valid update syntax. $inc operates atomically on each affected document and can be used with positive or negative numeric increments. Therefore, the correct multi-document update is db.products.updateMany({color: " green " }, {$inc:{price:5}}), making C correct.

Study Guide reference/topic:MongoDB Architecture and Core Operations - updateMany(), update operators, filters, and $inc.

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