MongoDB C100DBA - MongoDB Associate Database Administrator(Based on MongoDB 6.0 and 7.0+)

db.collection.stats() returns statistics for a specific collection, including storage-related values that help a DBA understand that collection ' s disk footprint. Therefore, for a collection named order, db.order.stats() is the relevant command among the choices. The result can include metrics such as logical data size, allocated storage size, document count, index information, and related collection statistics depending on version and storage engine. Option A, db.stats(), reports database-level statistics aggregated across the database rather than isolating the order collection. db.hostInfo(), option C, reports host and operating-system information rather than collection storage consumption. db.serverStatus(), option D, provides broad server-process runtime metrics such as connections, memory, operation counters, replication/storage-engine information, and other health data, but it is not the collection-specific disk-utilization interface requested here. Administrators can also use dedicated helpers such as collection storage-size or total-size methods when they need a more narrowly defined measurement. For a general collection-level statistics query targeting order, however, db.order.stats() is the correct answer, making option B correct.

Study Guide reference/topic:Performance Monitoring and Tuning - collection statistics, storage utilization, db.collection.stats(), and database/server metrics.

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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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