🔍 Proxy vs Facade

✅ Purpose of Comparison

Both Proxy and Facade introduce intermediary objects that stand between the client and the actual processing logic.
Despite having similar structural roles, they serve entirely different design goals.
This comparison clarifies their distinct responsibilities and provides practical guidance for selecting the appropriate pattern.

✅ Comparison Overview

Aspect	Proxy	Facade
Purpose	Add control or additional logic around real access	Simplify access to a complex subsystem
Primary Use	Access control, lazy loading, caching, logging	Combine multiple operations under a unified interface
Structure	Implements the same interface as the real subject	Wraps multiple subsystems behind a single interface
Scope	One-to-one (single object proxy)	One-to-many (multiple operations exposed as one)
Client Awareness	Clients may not realize they're using a proxy	Clients clearly interact through the simplified facade
Extensibility	Easy to inject pre/post-processing logic	Internal changes do not affect the external interface

✅ Similarities

• Both act as wrapper objects that abstract access to other classes or systems
• Help simplify client-side code and promote loose coupling
• Often used to provide a controlled or simplified interface to internal components

✅ Key Differences

Aspect	Proxy	Facade
Primary Purpose	Access control, lazy loading, logging, caching, etc.	Unifying complex subsystems behind a simple API
Usage Timing	When access needs to be intercepted or deferred	When subsystem complexity should be hidden
Responsibility	Delegates directly to the real object (RealSubject)	Orchestrates multiple components and operations
Structure	Implements the same interface as the real object	Defines a new high-level interface
Extensibility	Easy to inject pre/post logic around operations	Easy to hide internal complexity from the outside

✅ When to Choose Which

• ✅ Need to wrap behavior around individual object access → Proxy
• ✅ Need to offer a unified interface to multiple subsystems → Facade
• ✅ Want to delay, cache, or log method calls → Proxy
• ✅ Want to hide subsystem complexity and offer simpler API → Facade

✅ UML Class Diagram

Proxy Pattern

Facade Pattern

✅ Practical Design Notes

• ✅ Proxy is best suited for controlling or enriching access to a single object, such as adding logging, security, caching, or lazy evaluation.
• ✅ Facade excels at hiding complexity by providing a high-level entry point that orchestrates multiple operations behind the scenes.
• ▶️ Example: Using a caching proxy for a network API → Proxy; creating a unified SDK interface for multiple internal services → Facade

✅ Summary

• Proxy is a control-layer wrapper used for access mediation or augmentation
• Facade is an integration-layer gateway used for simplifying complex subsystems
• While both use indirection, they differ fundamentally in intent and scope
• Choose based on whether the focus is controlling individual access (Proxy) or streamlining high-level usage (Facade)