AWS App Design, 3

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A commercial product should support differentiation by a key; it should load sets of subclasses for that key.  The key can be a customer, an account, a car model, a product.   This pattern has several forms - Abstract Factory, Factory of Factories, Inversion of Control, Dependency Injection but they share the same goal.

API pseudo-code for AbstractFactory:

createEngine(key='Tesla') {
   AbstactFactory af = new AbstractFactory()
   return af.createFactory(key).createEngine()
 }

AbstractFactory pattern eliminates error-prone branching ("if..else") logic.   The intermediate Factory class supports a stateful API:

Car car = createCar()

// maintains factory state between calls
CarFactory tf = af.createFactory('Tesla')
car.engine = tf.createEngine()
car.axle = tf.createAxle()

AD1: Infrastructure with Cloud Formation
AD2: Messaging I/O
AD3: Abstract Factory
AD4: Database
AD5: Application Layer - Aspects
AD5: Application Layer - Canonical
AD5: Application Layer - Data Mapping
AD5: Application Layer - Protocol Adapter
AD6: Security