MongoDB Interview Questions - Interview Tips

Write a MongoDB Aggregation Pipeline

Create an aggregation pipeline to find the average age of users grouped by their city.

Expected output: A pipeline that groups users by city and calculates average age per city.

Hint: Use $group stage with $avg accumulator and $city field.

A document is a single record in MongoDB stored in BSON format, similar to a JSON object. A collection is a group of documents, analogous to a table in relational databases.

Indexing creates data structures that allow MongoDB to quickly locate documents without scanning the entire collection, significantly speeding up query execution.

The aggregation framework processes data records and returns computed results. It uses a pipeline of stages like $match, $group, and $sort to transform and aggregate data efficiently.