06 MongoDB

Question 1

span_0“What does ‘NoSQL’ stand for in the context of MongoDB?”

Answer 1

The name is considered misleading; it generally refers to non-relational databases that don’t follow strict SQL schemasspan_0.

Question 2

span_1“What are the main drawbacks of relational databases mentioned in the PDF?”

Answer 2

Constantly changing schemas, difficult data migrations, and performance/scalability issues due to strong consistencyspan_1.

Question 3

span_2span_3“Describe the system architecture of MongoDB.”

Answer 3

A client uses a driver to communicate with the ‘mongod’ process via a ‘wire protocol’ using JSON format for data and queriesspan_2span_3.

Question 4

span_4“List the logical structure of MongoDB from largest to smallest unit.”

Answer 4

Cluster -> Database -> Collection -> Documentspan_4.

Question 5

span_5“What is a ‘Document’ in MongoDB?”

Answer 5

The basic unit of storage, containing key-value pairs in JSON/BSON format, limited to 16MBspan_5.

Question 6

span_6span_7“What is a ‘Collection’ analogous to in a relational database?”

Answer 6

A Tablespan_6span_7.

Question 7

span_8“What is the maximum size of a single MongoDB document?”

Answer 7

16MBspan_8.

Question 8

span_9span_10“What is the mandatory field in every MongoDB document?”

Answer 8

The _id fieldspan_9span_10.

Question 9

span_11“What are the components of a 12-byte ObjectId?”

Answer 9

4 bytes timestamp (seconds), 5 bytes random (node + process ID), and 3 bytes counterspan_11.

Question 10

span_12span_13“What is ‘Denormalization’ in MongoDB?”

Answer 10

The practice of nesting or embedding related data within a single document instead of using separate tables and joinsspan_12span_13.

Question 11

span_14“How should 1-1 connections typically be handled in MongoDB schema design?”

Answer 11

Through nesting (embedding sub-documents)span_14.

Question 12

span_15“How can 1-many connections be represented in MongoDB?”

Answer 12

Either as an array embedded within a document or as a reference to another document’s _idspan_15.

Question 13

span_16“What does BASE stand for in NoSQL transactions?”

Answer 13

Basically Available, Soft State, Eventual Consistencyspan_16.

Question 14

True or False: MongoDB supports ACID transactions.

Answer 14

True. span_17span_18While typical NoSQL uses BASE, MongoDB has supported ACID transactions since version 4.0span_17span_18.

Question 15

span_19“What is the performance impact of using distributed transactions in MongoDB?”

Answer 15

Performance degrades significantlyspan_19.

Question 16

span_20“Which NuGet package is used for MongoDB in .NET?”

Answer 16

MongoDB.Driverspan_20.

Question 17

span_21“What does the [BsonId] attribute do in a C# class?”

Answer 17

It maps a specific property to the MongoDB ‘_id’ fieldspan_21.

Question 18

span_22“What does the [BsonElement(‘name’)] attribute do?”

Answer 18

It specifies the exact name of the field as it should appear in the MongoDB documentspan_22.

Question 19

span_23“What does the [BsonIgnore] attribute do?”

Answer 19

It tells the driver to skip that field when saving the object to the databasespan_23.

Question 20

span_24“What is a ‘Cursor’ in the context of querying?”

Answer 20

A way to process query results continuously rather than loading the entire list into memory at oncespan_24.

Question 21

span_25“What is the ‘Aggregation Pipeline’?”

Answer 21

A server-side process for multi-document operations like filtering, grouping, and countingspan_25.

Question 22

span_26“What is the equivalent of a ‘Left Outer Join’ in MongoDB aggregation?”

Answer 22

The $lookup functionspan_26.

Question 23

span_27“What is an ‘Upsert’ operation?”

Answer 23

An operation that updates a document if it matches a filter, or inserts a new one if no match is foundspan_27.

Question 24

span_28span_29“What is the difference between ReplaceOne and UpdateOne?”

Answer 24

ReplaceOne replaces the entire document with a new one (except ID), while UpdateOne modifies specific fieldsspan_28span_29.

Question 25

[span_30](start_span)"What does the $inc operator do?"

Answer 25

Increases the value of a numeric field by a specified amount[span_30](end_span).

Question 26

[span_31](start_span)"What does the $unset operator do?"

Answer 26

Deletes a specific field (key and value) from a document[span_31](end_span).

Question 27

[span_32](start_span)"What does the $push operator do?"

Answer 27

Adds a value to the end of an array[span_32](end_span).

Question 28

What is the difference between $push and $addToSet?

Answer 28

$push adds a value regardless of existence; [span_33](start_span)$addToSet only adds it if it doesn't already exist[span_33](end_span).

Question 29

T/F: MongoDB database names are case-insensitive.

Answer 29

False. [span_34](start_span)Database names are case sensitive and typically lowercase[span_34](end_span).

Question 30

T/F: Keys in a MongoDB document are case-sensitive.

Answer 30

True. [span_35](start_span)Document keys are case-sensitive[span_35](end_span).

Question 31

T/F: You can define a compound primary key in MongoDB.

Answer 31

False. [span_36](start_span)There are no compound keys, but you can use compound indices[span_36](end_span).

Question 32

T/F: A document key can begin with the '$' character.

Answer 32

False. [span_37](start_span)Keys cannot begin with the character $[span_37](end_span).