Back-End Development Database Design and Optimization 3

Question 1

What is the difference between SQL and NoSQL databases?

Accepted Answer

SQL databases use tables and schemas with ACID guarantees; NoSQL databases use flexible data models optimized for scale and specific access patterns

Answer

SQL is faster than NoSQL in all scenarios

Answer

NoSQL databases cannot store relationships between data

Answer

SQL is for small datasets; NoSQL is only for big data

Question 2

What is eventual consistency in distributed databases?

Accepted Answer

A model where data updates propagate to all nodes over time, and replicas are temporarily out of sync

Answer

The guarantee that all transactions are immediately consistent

Answer

The process of periodically cleaning up stale database records

Answer

A consistency level where only the master node is ever consistent

Question 3

What is a stored procedure in a relational database?

Accepted Answer

A precompiled set of SQL statements stored in the database that can be executed with a single call

Answer

A method of storing blobs in the database

Answer

A scheduled backup procedure

Answer

A way to store query results in a temporary table

Question 4

What is database replication and what problem does it solve?

Accepted Answer

Synchronizing data across multiple database instances to improve availability, read scalability, and fault tolerance

Answer

Copying a database schema to a new server

Answer

Creating database backups on a schedule

Answer

Duplicating tables within the same database for testing

Question 5

What is query caching and when should it be used?

Accepted Answer

Storing the results of expensive or frequently repeated queries in memory to avoid re-executing them against the database

Answer

Saving query source code in a version control system

Answer

Pre-compiling SQL queries at application startup

Answer

Caching database schema information in the application

Question 6

What is a database migration and why is it important in back-end development?

Accepted Answer

A versioned, incremental script that modifies the database schema in a controlled, repeatable way

Answer

Moving a database from one physical server to another

Answer

Exporting all database data to a CSV file

Answer

Converting data between SQL and NoSQL formats