CQRS Booking

You should implement a simple booking solution in CQRS architecture.

About CQRS

CQRS for Command Query Responsibility Segregation Pattern.

A query returns data and does not alter the state of the object. A command changes the state of an object but does not return any data.

We will split our code in read and write code to really live this pattern.

Booking subject

We want to make a booking solution for one hotel.

The first 2 user stories are :

• As a user I want to see all free rooms.
• As a user I want to book a room.

They want to use the CQRS pattern. To do that we will have :

• One Command Service with a function bookARoom(Booking)
  • that calls the WriteRegistry
  • that notifies the ReadRegistry called by the Query Service
• One Query Service with function Room[] freeRooms(arrival: Date, departure: Date)

The Booking struct contains

• client id
• room name
• arrival date
• departure date

And the Room struct contain only

• room name

Source

• inspiration source of this kata : https://github.com/tpierrain/CQRS/
• explanation of CQRS by Microsoft https://docs.microsoft.com/en-us/previous-versions/msp-n-p/jj591573(v=pandp.10)