This document discusses whether to refactor or rewrite existing code. It notes that all startups initially create legacy code. While rewriting from scratch has advantages like using new technologies, it also has disadvantages like losing features and taking a long time. Refactoring has benefits like maintaining existing knowledge and lower risk, but it is also painfully slow. The document provides questions to consider around timelines and features to help determine whether to refactor or rewrite. It concludes that rewriting is preferable only if there will be new features and it can be completed in under 6 months to minimize risk and impact.

1. FlixMobility
Rewrite or Refactor That Is the Question
Vladimir Jovanović
vladimirj.dev
@VladimirWrites

2. @VladimirWrites

3. @VladimirWrites

4. @VladimirWrites
PAINFUL TO WORK ON
SLOW
ONBOARDING
BUGS
SLOW DEVELOPMENT
TODOs

5. @VladimirWrites
PAINFUL TO WORK ON
SLOW
ONBOARDING
BUGS
SLOW DEVELOPMENT
TODOs
PAINFUL TO WORK ON
SLOW
ONBOARDING
BUGS
SLOW DEVELOPMENT
TODOs

6. @VladimirWrites
PAINFUL TO WORK ON
SLOW
ONBOARDING
BUGS
SLOW DEVELOPMENT
TODOs
PAINFUL TO WORK ON
SLOW
ONBOARDING
BUGS
SLOW DEVELOPMENT
TODOs
OBJECTIVE-C

7. @VladimirWrites
• Founded in 2013 in Germany
• It expanded rapidly in the EU
market
• 2018 – started operating in the
US
• Provides:
• network planning
• marketing
• pricing
• quality management
• and customer service to our
partner companies

8. @VladimirWrites
In 7 figures
>10,000
Drivers @partners
Countries
30 >2,500
Destinations
>400,000
Daily connections
Total passengers
>100m >500
Network partnersPlatform employees
>3000

9. @VladimirWrites
In 7 figures
>10,000
Drivers @partners
Countries
30 >2,500
Destinations
>400,000
Daily connections
Total passengers
>100m >500
Network partnersPlatform employees
>3000
CORONA

10. @VladimirWrites

11. @VladimirWrites

12. @VladimirWrites
All startup companies spend their first
years creating legacy code
And there is nothing wrong with it

13. @VladimirWrites

14. @VladimirWrites

15. @VladimirWrites

16. @VladimirWrites
REFACTOR REWRITE

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WE ARE THE SAME! OBJECTIVE-C

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6 months
Feature-freeze
Swift
Plan

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6 months
Feature-freeze
Swift
Plan
16 months
New features in
the old app
Features cut out
Objective-Cadded

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45+ modules
70% Kotlin
Trunk based
developmentRefactoring …

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Cons:
A lot of planning
No new features
No direct benefit to the
customers
Some features are lost
It takes longer than
expected
Huge risk
Pros:
Greenfield project
New technologies
Clean codebase
Pros:
Greenfield project
New technologies
Clean codebase
Rewrite

22. @VladimirWrites
Cons:
Painfully slow
Requires careful planning
Hard for developers
Refactoring
Pros:
Constant value
Not losing knowledge
Lower risk
Continuous user testing

23. @VladimirWrites
The total cost of refactoring is always
higher than doing a complete rewrite
but the impact on the organisation
is usually much smaller

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What should YOU do?

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It’s harder to read code than to write it
but it’s a bit easier to read it if you had written it

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I don’t like
the code style
It uses Framework
and not Framework
Java Sux!
I don’t understand
the codebase

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NO
Is the codebase really that bad?
YES
REFACTOR

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YES
Will there be new features?
NO
REFACTOR

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YES
Do you need more than 6 months?
NO
REFACTOR

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Can I rewrite the app now?
YES, BUT

32. THANK
YOU!

33. @VladimirWrites
Credits:
Articles:
• https://www.skcript.com/svr/rewrite-your-app-from-scratch/
• https://dev.to/rhymes/a-big-rewrite-5gl5
• https://daedtech.com/rewrite-or-refactor/
• https://gggritso.com/legacy-code
• https://ovid.github.io/articles/a-simple-way-to-fix-legacy-code.html
• https://www.joelonsoftware.com/2000/04/06/things-you-should-never-do-part-i/
Images:
• https://www.publicdomainpictures.net/en/view-
image.php?image=67199&picture=cooked-fresh-spaghetti
• https://emojipedia.org

34. @VladimirWrites
Vladimir Jovanović
vladimirj.dev
@VladimirWrites www.slideshare.net/VladimirWrites
QUESTIONS?