What is indexing in MongoDB?

Short answer: How is it different from SQL indexes? Indexing in MongoDB is a mechanism to improve query performance by reducing the amount of data the system needs to scan. MongoDB creates indexes on fields that are queried frequently. Differences from SQL indexes: MongoDB uses B-tree indexes (by default) but also supports other types like hashed indexes, geospatial indexes, and text indexes. SQL indexes are typically built on a…

Explain a bit more

fixed schema and are more rigid, while MongoDB indexes can be dynamic, allowing indexing on any field within a document. MongoDB supports compound indexes and array indexes for more complex queries.

Real-world example (ShopNest)

ShopNest adds an index on Orders(CustomerId, CreatedAt) because “my recent orders” is queried constantly.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.