Lightning talk Vertical vs Horizontal Software Architecture held at RubyConf India 2016 in Kochi, Kerala, India. Covers a few architecture principles to describe why vertical architectures are more maintainable than horizontal architectures.

1. Vertical vs Horizontal
Software Architecture
Christian Hujer
CEO / CTO Nelkinda Software Craft Pvt Ltd.
At RubyConf India 2016
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2. Horizontal Software Architecture
Directory structure reflects framework aspects
app/
┣━ controllers/
┣━ helpers/
┣━ models/
┣━ services/
┗━ views/
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3. Why it’s called “horizontal”?
Because the predominant architecture
represents (mostly) “horizontal” layers:
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views
helpers
controllers
services
models

4. Horizontal Architecture Synonyms
Horizontal Architecture
Layered Architecture
n-Tier Architecture
Multitier Architecture
Technical Architecture
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5. Bad Horizontal - Fundamentals
● Cohesion
● Coupling
● Design Smells, Immobility
● Communicating Intent
● CCP - Common Closure Principle
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6. Cohesion
Things that change together are cohesive.
Examples:
● A model, its view and and its controller.
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7. Collocation
Things which are “next” / “close” to each other.
Examples:
● Files in the same directory
● Classes in the same package
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8. The 4 Design Smells (Uncle Bob)
Design smells are the odors of rotting software.
● Rigidity
● Fragility
● Immobility
● Viscosity
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9. Immobility = Inability to Reuse
Reusable =
● Independently deployable
● Independently developable
● Independently testable
● Scalable (i.e. carving out microservices)
⇒ It’s important even if you don’t reuse!
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10. Oh, this is an MVC web application
(Surprise, surprise!)
vs
Oh, this is an event registration system.
Software Architecture
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11. Communicate Intent!
Like every software entity,
the architecture should
communicate its intent,
not its implementation!
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12. CCP: Common Closure Principle
“Classes that change together are packaged
together.”
From the 11 (sic!) “SOLID” principles
Design Principles and Design Patterns (Robert
C. Martin, 2000)
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13. CCP: Cohesion Collocation Principle
Cohesive things should be collocated!
Put things that change together in the same
place!
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14. Vertical Software Architecture
Directory structure reflects business aspects
app/
┣━ attendee/
┣━ event/
┣━ organizer/
┣━ payment/
┗━ subscription/
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15. Vertical Software Architecture
Directory structure reflects business aspects
app/
┣━ booking/
┣━ cleaning/
┣━ guest/
┣━ payment/
┗━ room/
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16. Let’s talk business!
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17. This talks Business!
app/
┣━ car/
┣━ driver/
┣━ insurance/
┣━ rental/
┗━ repair/
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18. This doesn’t talk Business!
app/
┣━ controllers/
┣━ helpers/
┣━ models/
┣━ services/
┗━ views/
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19. MVC is a pattern!
Pattern ≠ Architecture
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20. Architecture /
Directory Structure
Should Reflect
The Business Model
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21. MVC isn’t bad
But…
it shouldn’t dominate you
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22. Vertical Software Architecture
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car driver insurance rental repair

23. Thank you!
Follow me on Twitter
@christianhujer
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