Anti-patterns to avoid in LLD - Architecture Diagram

System Overview - Anti-patterns to avoid

This system overview explains common anti-patterns to avoid in system design. These anti-patterns cause poor scalability, reliability, and maintainability. Understanding them helps build better systems.

Architecture Diagram

User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  +-------------------+-------------------+
  |                   |                   |
Service A          Service B           Service C
  |                   |                   |
Cache A            Cache B             Cache C
  |                   |                   |
Database A         Database B          Database C

Components

User

user

Initiates requests to the system

Load Balancer

load_balancer

Distributes incoming requests evenly to API Gateway instances

API Gateway

api_gateway

Routes requests to appropriate backend services and handles authentication

Service A

service

Handles specific business logic for feature A

Service B

service

Handles specific business logic for feature B

Service C

service

Handles specific business logic for feature C

Cache A

cache

Stores frequently accessed data for Service A to reduce database load

Cache B

cache

Stores frequently accessed data for Service B to reduce database load

Cache C

cache

Stores frequently accessed data for Service C to reduce database load

Database A

database

Stores persistent data for Service A

Database B

database

Stores persistent data for Service B

Database C

database

Stores persistent data for Service C

Request Flow - 11 Hops

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Service A

Service A → Cache A

Cache A → Service A

Service A → Database A

Database A → Service A

Service A → Cache A

Service A → API Gateway

API Gateway → Load Balancer

Load Balancer → User

Failure Scenario

Component Fails:Cache A

Impact:Cache misses increase, causing more database queries and higher latency

Mitigation:System falls back to database queries; add cache replication or fallback caches to reduce impact

Architecture Quiz - 3 Questions

Which component prevents users from connecting directly to the database?

A Cache

B API Gateway

C Load Balancer

D Service

Design Principle

This architecture shows how separating concerns with load balancers, API gateways, caches, and services avoids common anti-patterns like direct database access, single points of failure, and tight coupling. Using caches reduces database load and improves response times, while load balancers and API gateways ensure scalability and security.

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