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MongoDB
MongoDB Certified DBA Associate
C100DBA
MongoDB Associate Database Administrator(Based on MongoDB 6.0 and 7.0+) Questions and Answers

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Viewing questions 51-60 out of questions

Questions # 51:

Which TWO indicators should an administrator keep an eye on to determine if the storage capacity is nearing its limit?

Options:

The execution time of the same query increases over time.

Disk space utilization on the server is consistently above 90%.

The number of documents in the database is increasing.

Message errno:28 No space left on device is present in the log file.

The number of available read or write tickets is consistently low.

Answer

B, D

Explanation

The most direct evidence that storage capacity is approaching exhaustion is high filesystem utilization and explicit operating-system errors showing that no space remains. Sustained disk utilization above 90% is a practical warning threshold because the deployment has little headroom for database growth, index builds, temporary files, journal activity, or operational spikes. The errno:28 No space left on device message is even stronger evidence: the operating system rejected a write because the relevant filesystem could not allocate additional space. The other choices can correlate with workload growth but do not specifically prove a capacity problem. Query execution time can increase because of poor indexes, cache misses, lock or ticket contention, or CPU pressure. A rising document count says nothing about remaining free space without knowing document size, index size, and volume capacity. Low read/write ticket availability reflects storage-engine concurrency pressure rather than filesystem capacity. Administrators should therefore monitor disk-used and disk-free metrics, alert well before full utilization, and investigate any ENOSPC-style log events immediately. B and D are the two storage-capacity indicators.

Study Guide reference/topic:Performance Monitoring and Tuning - disk capacity, storage metrics, alerts, and diagnostic logs.

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Questions # 52:

Which of the following command inside aggregate command is used in MongoDB aggregation to filter the documents to pass only the documents that match the specified condition(s) to the next pipeline stage.

Options:

$aggregate

$sum

$match

$group

Answer

Questions # 53:

What does the totalKeysExamined field returned by the explain method indicate?

Options:

Number of documents that match the query condition

Number of index entries scanned

Details the completed execution of the winning plan as a tree of stages

Number of documents scanned

Answer

Questions # 54:

Which of the following node is used during election in a replication cluster?

Options:

primary

arbiter

hidden

secondary

Answer

Questions # 55:

Consider the following document from the products collection:

Question # 55

What does the following query using $elemMatch return? db.products.find( { product_code: " 345678 " }, { variations: { $elemMatch: { size: ^L^ } } } )

Options:

Returns the complete document but retrieves only the size field from the array

Returns the document but with only one element in the variations array (corresponding to size L)

Returns the complete document since MongoDB does not support partial array retrieval

Returns the complete document but retrieves only the size field from the array and also with only one element in the variations array (corresponding to size L)

Answer

Questions # 56:

The difference between $push and $addToSet is:

Options:

$addToSet needs the fields to be already present while $push will work even if the field is not present

$addToSet adds the item to the field only if it does not exist already; while $push pushes the item to the field irrespective of whether it was present or not

$addToSet adds the item to the field only if the new item is of the same datatype

There is no major difference between them. $addToSet is a deprecated version of $push.

Answer

Questions # 57:

What is the on-premise solution having functionality equivalent to cloud manager?

Options:

Service Manager

Replica Manager

Ops Manager

Journaling

Answer

Questions # 58:

What are TWO functions of sharding?

Options:

Supporting deployments that distribute data across different geographical zones.

Supporting deployments that require strong consistency across geographical zones.

Supporting deployments with very large data sets and high throughput operations.

Supporting deployments where datasets fit into RAM and performance needs are met.

Supporting deployments that require redundancy and increased data availability.

Answer

A, C

Explanation

Sharding is MongoDB ' s horizontal-scaling mechanism: it partitions a collection ' s data across multiple shards so a deployment can scale storage capacity and distribute query or write workload beyond the limits of one server. That directly supports deployments with very large datasets and high-throughput operations, making C correct. MongoDB also supports zone sharding, which associates ranges of shard-key values with selected shards. Zones can be used to keep particular data near a geographical region, satisfy locality requirements, or map data ranges to hardware tiers, so A is also correct. Option B overstates what sharding itself provides; cross-region consistency behavior depends on replication topology, read/write concerns, latency, and application design rather than simply enabling sharding. Option D describes a deployment that already fits comfortably in memory and meets performance goals, so sharding may add unnecessary operational complexity. Option E primarily describes replication: replica sets maintain redundant copies, provide elections, and improve availability. Production shards are themselves normally replica sets, but redundancy is a replication function rather than the defining purpose of sharding. Therefore the two functions represented here are geographic zone distribution and horizontal scale: A and C.

Study Guide reference/topic:Sharding Strategies and Scalable Deployments - horizontal scaling, large datasets, throughput, shard keys, and zone sharding.

Questions # 59:

Which of the following are valid json documents? Select all that apply.