Event sourcing is a software design pattern that focuses on recording and preserving any changes to the state of an application as a series of events. Instead of storing an application's current state, event sourcing saves an event log or journal that describes each state change.
The state of an application is obtained through event sourcing by replaying and analyzing these events in the sequence in which they happened. This allows you to reconstruct an application's state at any time by applying the events in sequence. By storing events rather than the present state, you get a complete audit trail of how the application's state has grown over time.
The usual method in a financial application, for example, is to have a database; when a transaction is to be made, the program connects to the database, reads the account statement, and applies the changes as income or withdrawals.
With event sourcing, this process is not handled with the current state, but everything is derived in events. For example, instead of going to the database and modifying the account, the system issues an event with the details of this transaction, and the systems "interested" in this event will react and process the transaction.
Each transaction is classified as an event, and the program will explore each event to, for example, see the history of an account. It may appear to be extra effort, but the firm or client will have a history of everything that occurred as a security mechanism in case the database fails.
Event sourcing has various advantages:
It is crucial to note, however, that event sourcing is more complicated than standard state-based persistence. Event sourcing implementation necessitates careful planning and consideration of event storage, event playback methods, and eventual consistency handling.
Event sourcing is frequently used in areas that require auditability, traceability, or time analysis, such as financial systems, supply chain management, or complicated business operations. It can be used with other patterns, such as Command Query Responsibility Segregation (CQRS), to further separate an application's read and write sides.
Each event in the event feed typically reflects a single action or event in the system. These events are immutable, which means they cannot be changed once they have been registered. The events themselves collect pertinent information regarding the state change, such as the type of event, the entities affected, and any associated data.
We will discuss this topic and other event sourcing activities during our annual event on September 21 in Panama, where we will be joined by several of our global partners.
Our honored guests will be leaders from the banking, retail, insurance, and health industries, who will enjoy more than ten technical and commercial talks about the services we provide as a software development agency and the solutions provided by our partners: Red Hat, Acquia, ValidatedID, UiPath, and Microsoft.