Applied Designed Pattern

The UPS has evolved over time into a complex service with multiple components that adhere to current architecture and design patterns.

Firstly, the service relies on Event-Driven Design (EDD). In EDD, all events related to UPS are stored centrally. An event is an atomic occurrence that propagates a state change. In our case, an event could involve creating, deleting, or modifying an entity (e.g., a user). Data from this central source can be projected into any database and then retrieved. Projection transforms and stores input data into a database-specific format, significantly reducing access times as data doesn't need conversion during reads.

Next, the service follows the Command-Query-Responsibility-Segregation (CQRS) pattern. This pattern advocates for splitting object models into separate read and write parts within a database. The advantage of this pattern is improved scalability, as write operations can run on different hardware from read operations.

Furthermore, the UPS API supports the Asynchronous Request-Reply Pattern(ARRP). This pattern ensures that the API asynchronously handles data modification requests. The status of these modifications can be queried at any time using a dedicated endpoint. Communication in the command part between components is achieved through queuing. Retrieving an entity from the database still occurs via a REST call. Lastly, the UPS utilizes the Saga pattern, which simplifies data handling in distributed systems.