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

MongoDB exposes server parameters that can be configured through the parameter framework. Among the choices, --setParameter is the option specifically designed to set a server parameter on the mongod command line, using syntax such as mongod --setParameter < name > = < value > . A configuration file can also contain a setParameter section, but --config by itself merely tells mongod which configuration file to load; it is not the parameter-setting mechanism identified by the question. Connection-string options control how clients connect and cannot be used to configure arbitrary server runtime parameters. Option D is also incorrect because the server must already be running for mongosh to issue administrative commands. A technical nuance is important: parameters that support modification while the process is already running are changed with the administrative setParameter command, for example db.adminCommand({setParameter:1, ...}). Such runtime changes may not persist across a restart unless the value is also configured for startup. Given the options provided and the exam wording, --setParameter is the intended method, so A is correct.

Study Guide reference/topic:MongoDB Architecture and Core Operations - server parameters, --setParameter, configuration files, and runtime administration.

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The query contains equality predicates on both city and occupation, so an efficient compound index should contain both fields. Options A and C include only one query predicate plus the unrelated name field, forcing MongoDB to perform additional filtering that the index cannot resolve. Options B and D both contain the complete predicate set. For a query consisting entirely of equality predicates, MongoDB does not require those equality keys to appear in a particular order relative to one another for the query itself; { city: 1, occupation: 1 } and { occupation: 1, city: 1 } can both support the two equality conditions effectively. The original question appears to expect B because it mirrors the field order used in the query, but that distinction is not technically required under MongoDB ' s equality-key guidance. Field order becomes much more significant when the workload also needs a particular index prefix, sort order, range predicate, or when one ordering better supports additional common queries. Accordingly, the technically accurate review result is B and D, with B being the likely intended exam choice.

Study Guide reference/topic:Indexing and Query Optimization - compound indexes, equality predicates, and index key ordering.

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When MongoDB ' s winning query plan uses a B-tree index, the plan includes an IXSCAN stage. That stage contains the index-specific information a DBA needs to identify how the query is being serviced, including the key pattern, index name, traversal direction, and index bounds. For example, keyPattern can show a compound definition such as { status: 1, createdAt: -1 }, making it straightforward to confirm which indexed keys participate in the chosen plan. A FETCH stage indicates that MongoDB is retrieving full documents, often after an index has produced candidate record identifiers; the fetch stage itself does not identify the index key. A COLLSCAN stage means MongoDB is scanning the collection and therefore is not using a normal index scan for the predicate. GROUP is unrelated to index selection. Effective DBA query analysis usually involves inspecting both queryPlanner.winningPlan and execution statistics such as totalKeysExamined, totalDocsExamined, and nReturned. But for the narrow question of which stage exposes the index key used by the winning plan, IXSCAN is the correct answer. Therefore option C is correct.

Study Guide reference/topic:Indexing and Query Optimization - explain output, winning plans, IXSCAN, key patterns, and index bounds.

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For a compound index to satisfy a multi-field sort, the indexed fields must occur in the same sequence as the sort specification, and their directions must either match the requested pattern or be the complete reverse of it. The query sorts by { department: 1, salary: -1 }, so option B exactly matches both the key order and the requested directions. MongoDB can scan that index and return the results already ordered, avoiding a blocking in-memory sort. Option A uses { department: 1, salary: 1 }, which does not match the mixed-direction sort and is not its full inverse. Option D puts name before the two sort keys. Because the query has no equality predicate on name, that leading key prevents the later fields from directly providing the requested global sort. Option C is not a sensible index definition for this workload. Separately, the displayed projection mixes inclusion and exclusion (name:1, salary:1, department:0), which MongoDB normally disallows except for _id; that syntax issue should be corrected independently. It does not change the intended index answer for the sort, which is B.

Study Guide reference/topic:Indexing and Query Optimization - compound indexes, sort support, index prefixes, and key direction.

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