Introduction

Imagine your application has only 50 users during development. Everything works fine, and your database queries are fast.

A few months later, your application grows. Now, your users collection contains one million documents.

Suddenly, a simple login query starts taking several seconds:

db . users . find ({ email : " [email protected] " })

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The query looks simple, but MongoDB may need to check every document in the collection to find the matching email.

This is where indexing helps.

You can create an index on the email field with just one line:

db . users .…