Proxy pattern in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the Proxy Pattern Purpose

Which of the following best describes the primary purpose of the Proxy pattern in system design?

A To provide a placeholder for another object to control access to it

B To create multiple instances of an object to improve performance

C To directly modify the behavior of an object without changing its code

D To combine multiple objects into a single interface for easier use

💡 Hint

Think about how a proxy acts as a gatekeeper or representative.

The Proxy pattern provides a surrogate or placeholder for another object to control access to it, often adding additional behavior like lazy loading or access control.

❓ Architecture

intermediate

Proxy Pattern Components Identification

In a Proxy pattern architecture, which component is responsible for implementing the same interface as the real object and controlling access to it?

A Real Subject

B Proxy

C Client

D Adapter

💡 Hint

This component stands between the client and the real object.

The Proxy implements the same interface as the real object and controls access to it, acting as a middleman.

❓ scaling

advanced

Scaling a System Using Proxy Pattern

You have a system where creating the real object is expensive. Using the Proxy pattern, which approach best helps to scale the system efficiently?

A Use a Remote Proxy to replicate the real object on multiple servers

B Use a Protection Proxy to limit the number of clients accessing the real object

C Use a Virtual Proxy to delay the creation of the real object until it is needed

D Use a Cache Proxy to store multiple copies of the real object in memory

💡 Hint

Think about delaying expensive operations until absolutely necessary.

A Virtual Proxy delays the creation of the real object until it is actually needed, saving resources and improving scalability.

❓ tradeoff

advanced

Tradeoffs of Using Proxy Pattern

What is a common tradeoff when using the Proxy pattern in system design?

A Difficulty in testing because proxies cannot be replaced with mocks

B Reduced security because the proxy exposes internal details of the real object

C Loss of flexibility since the proxy cannot implement the same interface as the real object

D Increased complexity and potential performance overhead due to extra indirection

💡 Hint

Consider what extra step the proxy adds to method calls.

The Proxy pattern adds an extra layer of indirection which can increase complexity and cause some performance overhead.

❓ component

expert

Request Flow in Proxy Pattern

Given a Proxy pattern implementation, what is the correct sequence of components involved when a client requests a service?

A 1,2,3,4

B 1,3,2,4

C 2,1,3,4

D 1,2,4,3

💡 Hint

Think about the natural flow from client to proxy to real object and back.

The client first sends the request, the proxy receives and optionally checks it, then forwards it to the real subject, which processes and returns the response.