Mediator pattern in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the role of the Mediator

In a system using the Mediator pattern, what is the primary responsibility of the Mediator component?

A To replace all components with a single monolithic module

B To directly manage communication between components, reducing dependencies

C To store data persistently for all components

D To handle user interface rendering only

💡 Hint

Think about how components communicate without knowing each other directly.

The Mediator acts as a central hub that manages communication between components, helping to reduce tight coupling.

❓ Architecture

intermediate

Identifying components in a Mediator architecture

Which of the following best describes the components involved in a Mediator pattern architecture?

A Components communicate only through a central Mediator object that coordinates interactions

B Multiple components communicate directly with each other without any central controller

C A single component handles all logic and no communication is needed

D Components communicate through a shared global variable

💡 Hint

Focus on how communication is controlled in the pattern.

The Mediator pattern uses a central object to coordinate communication, preventing components from referring to each other directly.

❓ scaling

advanced

Scaling challenges with the Mediator pattern

What is a common scalability challenge when using the Mediator pattern in a large system?

A The Mediator can become a bottleneck as it handles all communication, increasing complexity

B Components become tightly coupled to each other, making changes difficult

C The system requires multiple Mediators to communicate directly with each other

D The Mediator pattern eliminates the need for any communication between components

💡 Hint

Consider what happens when one component handles all communication in a big system.

As the Mediator handles all interactions, it can grow complex and slow down the system if not designed carefully.

❓ tradeoff

advanced

Tradeoffs of using the Mediator pattern

Which tradeoff is true when applying the Mediator pattern in system design?

A It always improves performance by removing all indirect communication

B It simplifies the Mediator but increases dependencies between components

C It eliminates the need for any communication logic in the system

D It reduces component dependencies but can increase the complexity of the Mediator itself

💡 Hint

Think about what shifts when communication is centralized.

The pattern reduces direct dependencies but moves complexity into the Mediator, which must handle all coordination.

❓ component

expert

Request flow in a Mediator pattern system

Consider a chat application using the Mediator pattern where users send messages through a central chat room mediator. Which sequence correctly describes the request flow when User A sends a message to User B?

A 1,3,2,4

B 2,1,3,4

C 1,2,3,4

D 1,4,2,3

💡 Hint

Follow the logical order of message sending and receiving through the mediator.

The correct flow starts with User A sending the message to the Mediator, which then identifies the recipient and forwards the message, finally User B receives it.