Full-Stack Development Full-Stack Development Backend Systems & API Design 2

Question 1

What is the primary difference between SQL and NoSQL databases?

Accepted Answer

SQL databases use structured tables with schemas; NoSQL databases use flexible document or key-value models

Answer

SQL databases enforce a rigid schema with relational tables and ACID transactions, while NoSQL databases offer flexible schemas suited for hierarchical or unstructured data.

Question 2

In a relational database, what does a foreign key enforce?

Accepted Answer

Referential integrity by ensuring a value in one table matches an existing primary key in another

Answer

A foreign key constraint ensures that a value in a child table's column must correspond to an existing row in the referenced parent table, maintaining referential integrity.

Question 3

What is an ORM (Object-Relational Mapper) used for in backend development?

Accepted Answer

Mapping database tables to programming language objects so developers can query the DB with code instead of raw SQL

Answer

ORMs like Sequelize, Prisma, or TypeORM abstract database tables into classes/objects, letting developers perform CRUD operations using their language's syntax.

Question 4

What does database indexing primarily improve?

Accepted Answer

Read performance for query lookups on indexed columns

Answer

An index creates a data structure that allows the database to find rows matching a WHERE clause without scanning the entire table, drastically speeding up reads.

Question 5

Which MongoDB query operator finds documents where a field's value is in a given array?

Accepted Answer

$in

Answer

$in selects documents where the field value equals any value in the provided array, equivalent to SQL's IN clause.

Full-Stack Development Practice Test

Full-Stack Development Practice Test

Full-Stack Development Full-Stack Development Backend Systems & API Design 2