Facade pattern in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Purpose of the Facade Pattern

What is the main purpose of using the Facade pattern in system design?

A To replace all subsystem classes with a single class

B To enforce strict access control on all system components

C To provide a simplified interface to a complex subsystem

D To increase the number of classes for better modularity

💡 Hint

Think about how a facade helps users interact with complex systems.

The Facade pattern provides a simple interface to a complex set of classes or subsystems, making it easier for clients to use the system without dealing with its complexity.

❓ Architecture

intermediate

Identifying Facade Components

In a system using the Facade pattern, which component acts as the facade?

A A class that directly interacts with multiple subsystem classes and exposes a simple interface

B A low-level subsystem class that handles detailed operations

C A utility class that provides helper functions unrelated to subsystems

D A client class that uses the subsystem classes directly

💡 Hint

Consider which class hides complexity from the client.

The facade class wraps multiple subsystem classes and provides a simple interface for clients to interact with the system.

❓ scaling

advanced

Scaling a System with Facade Pattern

You have a large system with many subsystems. How does using the Facade pattern help when scaling the system?

A It forces clients to manage subsystem dependencies directly for better control

B It duplicates subsystem classes to handle more requests simultaneously

C It removes the need for subsystems, replacing them with a single facade class

D It reduces the number of client-subsystem interactions, making scaling easier by centralizing access

💡 Hint

Think about how centralizing access affects system complexity and scaling.

The facade centralizes subsystem access, reducing client complexity and making it easier to manage and scale the system.

❓ tradeoff

advanced

Tradeoffs of Using Facade Pattern

What is a potential tradeoff when using the Facade pattern in a complex system?

A It increases the number of classes, making the system harder to understand

B It can hide important subsystem features, limiting client flexibility

C It forces clients to interact with subsystems directly, increasing complexity

D It eliminates the need for subsystem classes, reducing modularity

💡 Hint

Consider what might be lost when simplifying interfaces.

While the facade simplifies usage, it may hide some subsystem features that clients might need, reducing flexibility.

❓ component

expert

Request Flow in Facade Pattern

Consider a facade class that coordinates three subsystems: A, B, and C. A client calls a facade method that internally calls methods in these subsystems. What is the correct sequence of calls if the facade first calls subsystem A, then B, then C?

A 1,2,3,4,5,6,7

B 1,3,5,2,4,6,7

C 7,1,2,3,4,5,6

D 2,1,4,3,6,5,7

💡 Hint

Think about the order of calls and completions in a synchronous flow.

The facade calls subsystem methods in order, waits for each to complete, then proceeds to the next, finally returning the result to the client.