Anti-patterns to avoid in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Identifying the God Object Anti-pattern

Which of the following best describes the God Object anti-pattern in system design?

A A pattern where data is stored in multiple redundant databases for fault tolerance.

B A design where multiple small classes each handle a single responsibility.

C A system design that uses microservices to distribute workload evenly.

D A single class or module that handles too many responsibilities, making the system hard to maintain.

💡 Hint

Think about what happens when one part of the system tries to do everything.

The God Object anti-pattern occurs when one class or module takes on too many roles, leading to complex, hard-to-maintain code.

❓ Architecture

intermediate

Recognizing Tight Coupling in System Components

Which option illustrates tight coupling between system components, an anti-pattern to avoid?

A Components directly depend on each other's internal implementations, making changes risky.

B Components are loosely connected via asynchronous messaging.

C Components communicate through well-defined interfaces and abstractions.

D Components are designed as independent microservices with clear APIs.

💡 Hint

Consider what happens when changing one component forces changes in others.

Tight coupling means components rely heavily on each other's internal details, causing fragility and difficulty in maintenance.

❓ scaling

advanced

Impact of the Spaghetti Code Anti-pattern on Scalability

What is the main scalability issue caused by the Spaghetti Code anti-pattern in system design?

A The code is tangled and unstructured, making it hard to isolate and scale individual components.

B The system uses too many microservices, causing overhead in communication.

C The system relies on caching, which can cause stale data issues.

D The database schema is normalized, leading to complex joins.

💡 Hint

Think about how messy code affects the ability to grow parts of the system.

Spaghetti Code is tangled and lacks clear structure, making it difficult to separate and scale parts of the system independently.

❓ tradeoff

advanced

Tradeoff of Premature Optimization Anti-pattern

What is a common negative tradeoff when applying premature optimization in system design?

A It always improves system performance with no downsides.

B It increases complexity and development time without significant performance benefits.

C It reduces code readability but improves scalability automatically.

D It simplifies the codebase by removing unnecessary features early.

💡 Hint

Consider what happens when you optimize before understanding the real bottlenecks.

Premature optimization can make code complex and harder to maintain, often wasting time on parts that don't impact performance much.

❓ component

expert

Detecting the Bottleneck in a Monolithic Architecture

In a monolithic system where the database becomes a bottleneck, which anti-pattern is most likely causing this issue?

A Microservices with independent databases causing data inconsistency.

B Event-driven architecture causing delayed responses.

C Single Point of Failure due to centralized database handling all requests.

D Load balancing distributing requests evenly across multiple databases.

💡 Hint

Think about what happens when one component handles too much traffic alone.

A monolithic system with a single database can create a single point of failure and bottleneck, limiting scalability and reliability.

Practice

1. Which of the following best describes the God Object anti-pattern in system design?

easy

A. Separating data storage and business logic into different layers.

B. A system design where components are loosely connected and communicate via events.

C. A single component that handles too many responsibilities, making the system hard to maintain.

D. Using multiple small services to handle different tasks independently.

Solution

1. Step 1: Understand the God Object concept and compare options

   The God Object anti-pattern occurs when one component or class takes on too many responsibilities, leading to complex, hard-to-maintain code. A single component that handles too many responsibilities, making the system hard to maintain. matches this description exactly, while others describe good design practices.

2. Final Answer:

   A single component that handles too many responsibilities, making the system hard to maintain. -> Option C

3. Quick Check:

   God Object = Single overloaded component [OK]

Hint: God Object means one part does too much [OK]

Common Mistakes:

• Confusing God Object with microservices
• Thinking God Object is a good modular design
• Mixing God Object with event-driven architecture

2. Which of the following is an example of a hardcoding anti-pattern in system design?

easy

A. Storing configuration values directly inside the source code.

B. Using environment variables for configuration.

C. Separating configuration into external files.

D. Using feature flags to toggle functionality.

Solution

1. Step 1: Identify what hardcoding means and match options

   Hardcoding means embedding fixed values directly in the code, making changes difficult and error-prone. Storing configuration values directly inside the source code. shows storing config inside code, which is hardcoding. Others are best practices.

2. Final Answer:

   Storing configuration values directly inside the source code. -> Option A

3. Quick Check:

   Hardcoding = fixed values in code [OK]

Hint: Hardcoding means fixed values inside code [OK]

Common Mistakes:

• Confusing hardcoding with using environment variables
• Thinking external config files are hardcoding
• Mixing feature flags with hardcoding

3. Consider a system where all modules directly access a single shared database without any abstraction layer. What is the main anti-pattern here?

medium

A. Tight Coupling

B. God Object

C. Spaghetti Architecture

D. Event-Driven Design

Solution

1. Step 1: Analyze direct database access and identify the anti-pattern

   When modules directly access the database without abstraction, they become tightly coupled to the database schema. Tight Coupling means components depend heavily on each other, reducing flexibility and increasing maintenance difficulty.

2. Final Answer:

   Tight Coupling -> Option A

3. Quick Check:

   Direct DB access = Tight Coupling [OK]

Hint: Direct DB access causes tight coupling [OK]

Common Mistakes:

• Confusing tight coupling with God Object
• Thinking event-driven design fits here
• Mixing spaghetti architecture with tight coupling

4. You find a system where many components are tightly interconnected with complex dependencies, making it hard to change one without breaking others. What anti-pattern is this, and how can you fix it?

medium

A. God Object; merge all components into one big class.

B. Spaghetti Architecture; refactor to modular design with clear interfaces.

C. Hardcoding; move all values into source code.

D. Tight Coupling; remove all interfaces and use direct calls.

Solution

1. Step 1: Identify the anti-pattern from description and determine the fix

   Complex interdependencies causing fragility is typical of Spaghetti Architecture. Refactoring to modular design with clear interfaces reduces dependencies and improves maintainability.

2. Final Answer:

   Spaghetti Architecture; refactor to modular design with clear interfaces. -> Option B

3. Quick Check:

   Spaghetti Architecture = tangled dependencies [OK]

Hint: Tangled dependencies = spaghetti; modularize [OK]

Common Mistakes:

• Thinking God Object means merging components
• Confusing hardcoding with architecture issues
• Believing removing interfaces reduces coupling

5. A startup built a monolithic system with many hardcoded values and a God Object managing most logic. They want to scale and maintain it easily. What is the best approach to fix these anti-patterns?

hard

A. Ignore scalability and focus only on adding new features.

B. Keep the monolith but add more hardcoded values for speed.

C. Merge all logic into one bigger God Object for simplicity.

D. Refactor into microservices, externalize configuration, and split responsibilities into smaller components.

Solution

1. Step 1: Identify problems in current system and choose best solution to fix anti-patterns

   Monolith with hardcoded values and God Object causes poor scalability and maintainability. Refactoring into microservices splits responsibilities, externalizing config removes hardcoding, improving scalability and maintainability.

2. Final Answer:

   Refactor into microservices, externalize configuration, and split responsibilities into smaller components. -> Option D

3. Quick Check:

   Microservices + external config fix anti-patterns [OK]

Hint: Split monolith, externalize config, avoid God Object [OK]

Common Mistakes:

• Thinking bigger God Object improves simplicity
• Adding more hardcoding for speed
• Ignoring scalability needs