MongoDB Associate Developer Most trusted Questions 2023
MongoDB Associate Developer Most trusted Questions 2023
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Question 1:
In MongoDB, what is the purpose of the “Array“data type?
A. To store a list of values with a consistent data type.
B. To store a list of values with inconsistent data types.
C. To store a single, scalar value.
D. To store a hierarchical structure of values.
Answer: B
Explanation:
To store a list of values with inconsistent data types. -> Correct. In MongoDB, the “Array“data type is used to store a list of values with inconsistent data types. Unlike relational databases, MongoDB allows documents to have fields with values of different data types, including arrays. This flexible data model allows for greater flexibility in storing complex data structures. For example, an array field in a document could store a mixture of strings, numbers, and other data types. Storing a single, scalar value, a list of values with a consistent data type, or a hierarchical structure of values would not provide the same level of flexibility as the “Array“ data type.
Question 2:
What is a recommended best practice for monitoring a MongoDB Atlas cluster?
A. Enabling Performance Advisor and Alerts in Atlas.
B. Regularly reviewing log files for errors.
C. Not enabling any performance or resource monitoring.
D. Only monitoring the memory usage of the cluster nodes.
Answer: A
Explanation:
Enabling Performance Advisor and Alerts in Atlas. -> Correct. MongoDB Atlas provides a number of built-in monitoring and management tools to help monitor the performance and health of a cluster. One recommended best practice is to enable Performance Advisor and Alerts in Atlas. Performance Advisor provides recommendations for optimizing cluster performance and alerts can be configured to notify administrators of any performance or resource issues. Regularly reviewing log files for errors is also important for monitoring a MongoDB Atlas cluster, but it does not provide the same level of insight as Performance Advisor and Alerts. Not enabling any performance or resource monitoring, or only monitoring the memory usage of the cluster nodes, can result in performance issues going unnoticed, leading to decreased performance and potential data loss.
Question 3:
Which of the following must be true for a query to be a covered query? Check all that apply.
A. All fields used in the selection filter of the query must be in the index that the query uses
B. All fields returned in the results must be in the index that the query uses
C. All fields returned in the results must be fields in the selection filter of the query
Answer: A, B
Explanation:
All fields used in the selection filter of the query must be in the index, so the system can find the documents that satisfy the selection filter without having to retrieve the document from the collection.
All fields returned in the results must be in the index, so again there is no need to retrieve the full document. A common mistake is not to provide a projection that filters out the field _id, which is returned by default. If the _idfield is not a field in the index definition, it is not available, and the query system will need to fetch the full document to retrieve the value.
On the other hand, it is OK to ask for more fields than the ones provided in the selection filter, as long as those are in the index values, the system has all the information needed to avoid fetching the full document from the collection.
Question 4:
Suppose you have a MongoDB collection called locations that contains documents with the following structure:
{
_id: ObjectId,
name: String,
location: {
type: String,
coordinates: [Number]
}
}
You want to find all documents within a 10 km radius of a point with latitude 40.7128 and longitude -74.0060. Which of the following queries would you use?
A. db.locations.find({location: {$near: [40.7128, -74.0060], $maxDistance: 10000}})
B. db.locations.find({location: {$geoWithin: {$centerSphere: [[40.7128, -74.0060], 10 / 3963.2]}}})
C. db.locations.find({location: {$geoIntersects: {$geometry: {type: “Point“, coordinates: [40.7128, - 74.0060]}, $maxDistance: 10000}}})
D. db.locations.find({location: {$nearSphere: [40.7128, -74.0060], $maxDistance: 10}})
Answer: B
Explanation:
Option b is the correct query for finding all documents within a 10 km radius of a point with latitude 40.7128 and longitude -74.0060. This query uses the $geoWithin operator with the $centerSphere option, which takes an array of two elements: the center point in longitude and latitude, and the radius in radians. In this case, the radius is calculated as 10 km divided by the radius of the Earth in miles (3963.2 miles). Option a uses the $near operator, which is similar to $geoWithin but does not take into account the spherical shape of the Earth. Option c uses the $geoIntersects operator, which checks whether a shape intersects with a geospatial object but does not allow for a radius. Option d uses the $nearSphere operator, which is similar to $near but takes into account the spherical shape of the Earth. However, the maximum distance is specified in radians, not kilometers.
Question 5:
What is a common security threat to a MongoDB database?
A. SQL injection attacks
B. Cross-site scripting (XSS) attacks
C. Buffer overflow attacks
D. Injection attacks targeting the MongoDB query language
E. None of the above
Answer: D
Explanation:
MongoDB databases are vulnerable to injection attacks where an attacker can inject malicious code into a query or command that is executed by the database. This can lead to data theft or manipulation, privilege escalation, and other security breaches.
SQL injection and buffer overflow attacks are not applicable to MongoDB because it does not use SQL or rely on the same types of memory management. Cross-site scripting attacks are a web-based vulnerability and are not directly related to the database itself.
hile buffer overflow attacks are not common against MongoDB databases, they are a general type of vulnerability that can affect any software that handles data. In theory, if an attacker can exploit a buffer overflow vulnerability in a MongoDB driver or server component, they could potentially execute arbitrary code or manipulate data in ways that were not intended. However, buffer overflow attacks are typically more difficult to execute against modern software systems that are designed with security in mind, and there are generally more effective and easier ways for attackers to compromise MongoDB databases.
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Question 6:
Which of the following steps are necessary for creating a MongoDB shard? (Select three)
A. Launch a mongos instance on each shard server.
B. Create a config server replica set.
C. Configure sharding for each collection.
D. Add mongod instances to the config server replica set.
E. Create a mongod instance for each shard.
F. Enable sharding on the config database.
Answer: B, C, E
Explanation:
The correct options are: B, C, and E.
B. Creating a config server replica set is necessary to store metadata about the cluster‘s configuration, such as sharding information and chunk ranges.
C. Configuring sharding for each collection is necessary to specify which collections should be sharded and on which shard key.
E. Creating a mongod instance for each shard is necessary to create a separate storage space and processing resources for the sharded data.
A. While launching a mongos instance on each shard server is recommended for performance and fault tolerance reasons, it is not strictly necessary to create a MongoDB shard.
D. Adding mongod instances to the config server replica set is not necessary for creating a MongoDB shard, as mongod instances are used to store the sharded data, not the metadata.
F. Enabling sharding on the config database is not necessary for creating a MongoDB shard, as sharding is typically enabled on individual collections, not on the entire database.
Question 7:
Which of the following is a necessary step when backing up a MongoDB shard?
A. Run the mongodump command on each shard server.
B. Run the mongodump command on each mongos server.
C. Run the mongodump command on a single mongos instance.
D. Run the mongodump command on the config server.
Answer: C
Explanation:
When backing up a MongoDB shard, you should run the mongodump command on a single mongos instance that is connected to the shard cluster. The mongos instance will coordinate the backup process by directing mongodump to connect to the appropriate shards and perform the backup.
A is incorrect because running mongodump on each shard server may result in inconsistent backups if documents are moved between shards during the backup process.
B is incorrect because mongosqldump is not a valid MongoDB backup command.
D is incorrect because running mongodump on the config server will only back up the metadata about the sharded cluster, not the actual data stored in the shards.
Question 8:
In a MongoDB replica set, what is the purpose of a hidden replica set member? Choose all that apply
A. to act as a secondary node that can serve read requests.
B. To provide a backup of the primary node
C. To act as a secondary node that cannot be used for read requests.
D. To prevent elections by being a non-voting member.
Answer: B, C
Explanation:
A hidden replica set member in MongoDB is a secondary node that is not eligible to serve read requests. It is useful for performing background tasks, such as analytics or backups, without affecting the performance of the primary and other secondary nodes. By designating a secondary node as hidden, the MongoDB replica set can prevent read requests from being directed to this node, thereby freeing up resources for other tasks. it can still be used as voting member.
Question 9:
What is MongoDB aggregation, and how can it be used to analyze data?
A. A tool for importing and exporting data between MongoDB and other databases
B. A method for indexing data in MongoDB for faster query performance
C. A way to combine and manipulate data from multiple documents in a MongoDB collection
D. A tool for managing database backups and restores in MongoDB
E. A technique for optimizing MongoDB cluster performance through load balancing
Answer: C
Explanation:
The correct answer is C) A way to combine and manipulate data from multiple documents in a MongoDB collection.
MongoDB aggregation is a powerful framework for analyzing and processing data stored in MongoDB. With aggregation, you can perform complex data analysis tasks such as grouping, filtering, sorting, and joining data from multiple documents in a MongoDB collection.
Option A is incorrect because MongoDB aggregation is not related to importing or exporting data between MongoDB and other databases.
Option B is incorrect because indexing is a separate feature in MongoDB that improves query performance by creating index structures to speed up queries on frequently accessed fields.
Option D is incorrect because backups and restores are not related to MongoDB aggregation. However, MongoDB does provide a separate backup and restore utility called mongodump and mongorestore.
Option E is incorrect because load balancing is a feature of MongoDB sharding, which is a separate feature from MongoDB aggregation.
Question 10:
Which of the following use cases can be addressed using the rs.reconfig command in MongoDB replication?
A. Changing the election timeout settings.
B. Removing many members from a replica set.
C. Changing the primary member of a replica set.
D. Changing the storage engine of a replica set.
Answer: A
Explanation:
The rs.reconfig command is used to modify the configuration of a MongoDB replica set. Some common use cases for this command include:
A) Changing the election timeout settings – This setting determines how long a replica set member should wait before triggering an election to select a new primary member. The rs.reconfig command can be used to modify this setting, for example, to prevent unnecessary elections during network disruptions or temporary outages.
B) Removing many member sfrom a replica set -Starting in MongoDB 4.4, rs.reconfig() allows adding or removing no more than 1 member at a time. To remove multiple members from the replica set, issue a series of rs.reconfig operations to remove one member at a time.
D) Changing the primary member of a replica set – This can be necessary in case the current primary member becomes unavailable or experiences issues. However, the rs.reconfig command itself does not change the primary member. Instead, the primary member is selected through an election process that is initiated automatically when the current primary member becomes unavailable.
E) Changing the storage engine of a replica set – The rs.reconfig command cannot be used to change the storage engine of a replica set. Instead, the storage engine must be changed by re-initializing the replica set with the desired storage engine.
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It is recommended to score above 85% in SkillCertPro exams before attempting a real exam.
SkillCertPro updates exam questions every 2 weeks.
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