Questions

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1What are indexes?

2How to create Indexes?

3On which filed you will create an index - projection field or filter field?

4What happens if I create an index on all fields of the collection?

5What is the difference between Single Field Indexes & Compound Indexes?

6How to list all indexes?

7How to drop an index?

8What is a 'Covered Query' and how do you design one using Projection?

9Explain the ESR (Equality, Sort, Range) rule. Why is the order of fields in a compound index so critical?

10What is a Sparse Index? Discuss its usage and advantages.

11What is a 'Partial Index' and when would you choose it over a 'Sparse Index'?

12How do indexes affect write performance in a collection that handles 5,000 inserts per second?

13Walk me through the output of .explain('executionStats'). What are the red flags for a senior dev?

14How do you handle 'Index Intersection'? Is it better to have two single-field indexes or one compound index?

15Explain the internal mechanics of a 'Multikey Index'. What happens if you index an array of 1,000 elements?

16How do TTL (Time-To-Live) indexes work and what are their limitations?

17When would you use a Hashed Index vs. a standard B-Tree index?

18You are scraping retail data. You need to query by category (string), sort by price (number), and filter by lastSeen (date range). How do you index this?

MongoDB

Bulk Operations

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What happens if I create an index on all fields of the collection?

Indexes are data structures that occupy space and memory in database. Therefore, it is beneficial to create indexes for fields that are frequently used in query conditions/ filtering or for sorting, as this can significantly improve query performance.