MEAN MongoDB Advanced Operations 3

Question 1

What is the purpose of MongoDB transactions introduced in version 4.0?

Accepted Answer

Provide ACID guarantees across multiple documents and collections

Answer

MongoDB multi-document transactions allow multiple reads and writes across documents, collections, and databases to execute with ACID properties.

Question 2

Which MongoDB command is used to initiate a replica set?

Accepted Answer

rs.initiate()

Answer

rs.initiate() is run from the mongo shell to initialize a replica set configuration on the primary node.

Question 3

In MongoDB, what does the $group aggregation stage do?

Accepted Answer

Groups documents by a specified expression and accumulates values

Answer

$group groups input documents by a specified _id expression and can apply accumulator operators like $sum, $avg, $max to each group.

Question 4

What is the default port MongoDB listens on?

Accepted Answer

27017

Answer

MongoDB's default port is 27017, while port 28017 was used by the deprecated HTTP monitoring interface in older versions.

Question 5

Which MongoDB feature allows data to automatically expire after a set time?

Accepted Answer

TTL (Time-To-Live) indexes

Answer

TTL indexes allow MongoDB to automatically delete documents after a specified number of seconds based on a date field in the document.

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