Software Architecture Pattern

Application Landscapes

Monolith

• Advantages
  • Easy to understand,implement,and test
  • Easy deployment
  • Ideal for limited scope
• Disadvantages
  • Tight coupling
  • Easily leads to complex code
  • One size fit all for every subdomain

N-tier

• Summary
  • Multiple tiers
  • Tier perform specific task
  • Tiers can be physically separated
  • Tiers aren’t layers
  • Technical boundaries
• Typical: 3 tier
  • Presentation Tier(UI & pure UI logic)
  • Business Logic Tier(business logic)
  • Data Tier
• Advantages
  • Independent development
  • Scalability
• Disadvantages
  • Changes ripple through tiers

Service-Oriented

• Summary
  • Multiple services
  • Each service is a business activity
  • Service compose-ability
  • Contract standardization
  • Enterprise Service Bus
• Advantages
  • Services are loosely coupled
  • Scalability
  • No duplication of functionality
• Disadvantages
  • Reduced agility and team autonomy
  • Costly
  • Many differing views

MicroServices

• Summary
  • Multiple services
  • Each service is a business activity
  • Teams run the service
  • No logic-heavy enterprise service bus
  • Maximum automate
• Advantages
  • Services are loosely coupled and easily scalable
  • Increased agility
  • Reliability
  • Designed to handle failures
• Disadvantages
  • Boundaries not always clear
  • Communication patterns can become complex

Serverless

• Summary
  • Backend as a service
  • Function as a service

peer-to-peer

• Summary
  • No central server
  • No constant connection
  • Dynamically discoverable
• Advantages
  • Share resources
  • Save cost
  • Scaling
• Disadvantages
  • possible security issues
  • Only for specific scenarios
  • Nontrivial to code

Application Structure Patterns

Layered

• Summary
  • Presentation(UI)
  • Application(Translation between UI & business)
  • Business(Business logic)
  • Persistence(Code to interact with the database)
  • Data(Data)
• Advantages
  • well-known among developers
  • Easy to organize
• Disadvantages
  • Can lead to monolithic applications
  • Need to write lots of code

Microkernel

• Summary
  • Task scheduler
  • Workflow
  • Data processing
  • Browser
  • Graphic designer
• Advantages
  • Flexibility
  • Clean separation
  • Separate teams possible
  • Add and remove functionality at runtime
• Disadvantages
  • Core API might not fit future plugins
  • Can the plugins be trusted
  • Not always clear what belongs in the core

CQRS

• Summary
  • Command Query Responsibility Segregation
  • 2 models: read/query & write/command
  • Allows for scenario-specific queries
  • Synchronization required
  • Different from event sourcing
• Advantages
  • Simpler read queries
  • Faster and more scalable read queries
  • Easier to communicate with stakeholders
• Disadvantages
  • Added complexity
  • Learning curve
  • Possibility of data inconsistencies
  • Eventual consistency

Event sourcing

• Summary
  • Store events instead of current state
  • Event = something that happened in the past
  • Rehydration or replay
• Advantages
  • Trace of events
  • Audit trail
  • Business language
  • Event replay
• Disadvantages
  • Replay and external systems
  • Event structure changes
  • Snapshots

CQRS and Event sourcing combined

• Summary
  • 2 different concepts
  • Powerful combination
  • It’s not for simple domains, you could start with event sourcing, then add CQRS later.
• Advantages
  • Simpler and fast queries
  • Scalable
  • Trace of event
  • Audit trail
  • Business language
• Disadvantages
  • Added complexity
  • Leaning curve
  • Data inconsistencies
  • Event structure change

UI Patterns

MVC

• Summary
  • Controller
  • Model
  • View
• Advantages
  • Separation of concerns
  • Parallel development
  • Popular in web frameworks
• Disadvantages
  • Controllers can become bloated
  • Different definitions

MVP

• Summary
  • View
  • Presenter
  • Model
• Advantages
  • Great for desktop application
  • Separation of concerns
  • Testability
• Disadvantages
  • Presenter can become bloated
  • Desktop application are less popular
  • MVVM Pattern

MVVM

• Summary
  • View
  • ViewModel
  • Model
• Advantages
  • Great for modern desktop and mobile applications
  • Separation of concerns
  • Testability
• Disadvantages
  • Overkill for user interfaces
  • More difficult to debug
  • Desktop applications are less popular

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