MongoDB Interview Questions and Answers
Experienced / Expert level questions & answers
Ques 1. How can you achieve ACID properties in MongoDB?
MongoDB sacrifices ACID properties for performance and scalability. However, it supports multi-document transactions in recent versions to some extent.
Ques 2. What is the use of the `explain` method in MongoDB?
The `explain` method provides information on the query execution plan, helping in optimizing and understanding how a query is executed.
Ques 3. Explain the concept of covered queries in MongoDB.
Covered queries are queries where all the fields in the query are part of an index, and the index itself can fulfill the query requirements, avoiding the need to fetch data from the actual documents.
Ques 4. What is the role of the `$lookup` stage in MongoDB aggregation?
The `$lookup` stage is used in MongoDB aggregation to perform a left outer join between documents from the source and target collections based on a specified condition.
Ques 5. What is the use of the `mongostat` command in MongoDB?
The `mongostat` command provides a real-time view of various MongoDB statistics, such as insert and query rates, memory usage, and more.
Ques 6. How does MongoDB handle transactions?
MongoDB supports multi-document transactions starting from version 4.0. Transactions allow you to perform multiple operations on one or more documents and ensure atomicity and consistency.
Ques 7. What is the Aggregation Pipeline in MongoDB?
The Aggregation Pipeline is a framework in MongoDB for data aggregation. It allows you to process data and transform it using a sequence of stages, such as `$match`, `$group`, and `$project`.
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