Prototype pattern in LLD - System Design Exercise

Design: Prototype Pattern Implementation

Focus on the design and implementation of the prototype pattern in a software system. Out of scope are UI details, persistence layers, and distributed system concerns.

Functional Requirements

FR1: Allow creation of new objects by copying existing ones (cloning).

FR2: Support deep and shallow copy options.

FR3: Enable customization of cloned objects without affecting the original.

FR4: Provide a registry to manage prototypes for easy access and cloning.

FR5: Ensure cloning is efficient to improve performance when creating many similar objects.

Non-Functional Requirements

NFR1: Cloning operations should have low latency (p99 < 50ms).

NFR2: Support up to 10,000 clone requests per minute.

NFR3: Maintain consistency so cloned objects do not share mutable state unintentionally.

NFR4: Design should be extensible to add new prototype types without major changes.

Think Before You Design

Questions to Ask

❓ Question 1

❓ Question 2

❓ Question 3

❓ Question 4

❓ Question 5

Key Components

Prototype interface or abstract class defining clone method

Concrete prototype classes implementing clone

Prototype registry or factory to store and retrieve prototypes

Client code that requests clones from the registry

Cloning mechanism supporting deep and shallow copies

Design Patterns

Prototype pattern for cloning objects

Factory pattern for managing prototype instances

Decorator pattern for customizing cloned objects

Singleton pattern for prototype registry management

Reference Architecture

Client
  |
  v
Prototype Registry (Singleton)
  |
  v
Concrete Prototypes (Cloneable)

Legend:
- Client requests clone from Prototype Registry
- Registry returns cloned object from stored prototype
- Cloning can be shallow or deep based on prototype implementation

Components

Prototype Interface

Abstract class or interface in chosen language

Defines the clone method signature for all prototypes

Concrete Prototype Classes

Classes implementing Prototype interface

Provide implementation of clone method for specific object types

Prototype Registry

Singleton class with a map/dictionary

Stores prototype instances and provides cloning access to clients

Client

Any application code

Requests clones from the registry instead of creating new objects

Request Flow

1. Client requests a clone of a specific prototype from the Prototype Registry.

2. Prototype Registry looks up the stored prototype instance.

3. Registry calls the clone method on the prototype instance.

4. Prototype returns a new cloned object (shallow or deep copy).

5. Client receives the cloned object and can customize it independently.

Database Schema

Not applicable as this is an in-memory design pattern implementation without persistent storage.

Scaling Discussion

Bottlenecks

Prototype Registry becoming a single point of contention under high clone request load.

Cloning complex objects with deep nested structures causing performance overhead.

Memory usage increasing due to many cloned objects held in memory.

Managing consistency when cloned objects share references to mutable nested objects.

Solutions

Use concurrent data structures or lock-free mechanisms for Prototype Registry to handle concurrent access.

Optimize clone methods to perform selective deep cloning only where necessary.

Implement object pooling or garbage collection tuning to manage memory efficiently.

Design prototypes to use immutable nested objects or implement deep cloning carefully to avoid shared mutable state.

Interview Tips

Time: Spend 10 minutes understanding requirements and clarifying questions, 20 minutes designing the prototype pattern components and data flow, 10 minutes discussing scaling and trade-offs, and 5 minutes summarizing.

Explain the purpose of the prototype pattern to create new objects by cloning.

Describe how the prototype registry simplifies object creation and management.

Discuss shallow vs deep cloning and their impact on object independence.

Highlight how this pattern improves performance by avoiding expensive object creation.

Mention potential bottlenecks and how to scale the design for high load.