Back-End Development Basics of Back End Development 4 — Questions and Answers
Question 1: What is the purpose of database indexing?
- To enforce data type constraints on columns
- To speed up data retrieval by creating a fast-lookup data structure (Correct answer)
- To replicate data to a secondary server automatically
- To compress table rows to reduce storage size
Correct answer: To speed up data retrieval by creating a fast-lookup data structure
An index creates an auxiliary data structure (often a B-tree) that allows the database engine to find matching rows without scanning the entire table.
Question 2: Which design pattern separates an application into three concerns: data, business logic, and presentation?
- Singleton
- Observer
- MVC (Model-View-Controller) (Correct answer)
- Factory
Correct answer: MVC (Model-View-Controller)
MVC divides responsibility into the Model (data/business logic), View (presentation), and Controller (input handling), making code easier to maintain and test.
Question 3: What does the term 'N+1 query problem' refer to in back-end development?
- Running one query to fetch a list and then one additional query per list item (Correct answer)
- Executing a query with more than N join conditions
- Sending N identical queries to N different database replicas
- Writing a query that returns N+1 rows due to an off-by-one error
Correct answer: Running one query to fetch a list and then one additional query per list item
The N+1 problem occurs when code fetches a list of N items and then lazily runs a separate query for each, resulting in N+1 total queries that could be replaced by a single JOIN or eager load.
Question 4: Which of the following is a key benefit of using a message queue (e.g., RabbitMQ, SQS) in a back-end system?
- It eliminates the need for a database
- It decouples producers and consumers, allowing asynchronous processing (Correct answer)
- It provides end-to-end encryption for all API calls
- It replaces HTTP as the transport protocol between services
Correct answer: It decouples producers and consumers, allowing asynchronous processing
Message queues allow services to communicate without being tightly coupled, letting producers and consumers operate at different speeds and fail independently.
Question 5: What is the purpose of a reverse proxy like Nginx in a back-end setup?
- Directly executing application code on behalf of the server
- Sitting in front of application servers to handle routing, SSL, and load balancing (Correct answer)
- Replacing the database layer with in-memory storage
- Converting HTTP requests to binary protocol for faster transmission
Correct answer: Sitting in front of application servers to handle routing, SSL, and load balancing
A reverse proxy receives client requests and forwards them to one or more backend servers, also handling SSL termination, caching, and load distribution.
Question 6: In the context of back-end APIs, what is rate limiting?
- Limiting the size of JSON payloads a server will accept
- Restricting the number of requests a client can make in a given time period (Correct answer)
- Capping the maximum query execution time in the database
- Throttling CPU usage per Node.js worker process
Correct answer: Restricting the number of requests a client can make in a given time period
Rate limiting controls how many requests a client (identified by IP, API key, or user) can make within a window, protecting the server from abuse and ensuring fair usage.
Question 7: Which data serialization format is most commonly used for REST API request and response bodies?
- XML
- CSV
- YAML
- JSON (Correct answer)
Correct answer: JSON
JSON (JavaScript Object Notation) is the dominant format for REST APIs due to its lightweight syntax, human readability, and native support in browsers and most languages.
Back-End Development Basics of Back End Development 4
What is the purpose of database indexing?