Never Change Running System

Architecture and code structurestub

Intent

To minimize risks, you should try to refrain from changes to existing (working) code - as every change inevitably introduces new risks or even bugs.

Front-End Switch stub
Route front-end requests to either new or old backend systems, depending on their nature, content-negotiation or other request criteria. This is especially helpful to support Never Change Running System.
Interface Segregation Principle
Reduce coupling between clients and service providers.
Keep Data, Toss Code stub
A strategy to improve systems, keeping the data created with the (old) systems as foundation for a new one. Also described as Bridge-to-the-New-Town (by Wolfgang Keller). This is the opposite of Never Change Running System.

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