What is the difference between a clustered and non-clustered index?

Short answer: Clustered Index: The data is stored in the order of the index. A table can have only one clustered index because the rows can only be ordered in one way. Non-clustered Index: The index is separate from the data, and the index contains pointers to the data. A table can have multiple non-clustered indexes.

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.