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event-sourcing

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Homework 3 (Second semester)

Goal: to gain practical experience in implementing event-sourcing systems and applying the principles of CQRS.

To implement an information system for a fitness center. The clients of the fitness center can buy and prolong their membership. When entering and leaving the fitness center, the client is obliged to attach a membership card for the passage. The system allows you to build a variety of reports based on statistics collected in the course of the service.

The system consists of three parts:

  1. Web service for a manager, allows to

  • View information about subscriptions (by number)

  • Issue and renew cards

  1. Reporting service, allows you to

  • View attendance statistics by day

  • Calculate the average frequency and duration of visits

  1. Input/output module

  • Lets the customer in if he has a valid season ticket

  • saves the client's entry/exit time in the database

Directions

  • The system should be based on an event-sourcing approach

  • Commands and requests must be strictly separated (CQRS-principle)

  • Events themselves should be stored in a persistent repository.

  • The service for the manager and the input/output module do not have a separate database, and when The request pulls all the events of the subscription from the storage of events, aggregating them on the fly.

  • The reporting service, on the contrary, calculates statistics on startup and stores them in memory, It is updated with the new events (but it is possible to store them in a separate persistent (but it is possible to store it in a separate persistent storage).

References