Key Concepts of Event Sourcing
- Events:
- Events represent meaningful occurrences or actions within a system.
- Each event captures specific information about the change that occurred, such as what happened when it happened and any relevant data associated with the event.
- Examples of events include “OrderPlaced,” “PaymentReceived” or “UserLoggedIn.”
- Event Log:
- The event log is a simple record of all events that have occurred in the system.
- It serves as the single source of truth in an event-sourced architecture by capturing the entire history of changes to the application’s state.
- The event log is immutable meaning that once an event is recorded, it cannot be changed or deleted.
- It provides a comprehensive audit trail of system activity, enabling detailed historical analysis and troubleshooting.
- Event Store:
- The event store is the database or storage mechanism used to persist events.
- It stores events in the order they occurred, ensuring that the chronological sequence of events is preserved.
- The event store provides functionalities for appending new events to the event log and retrieving events based on various criteria.
Benefits of Event Sourcing
Event sourcing offers several advantages over traditional state-centric approaches:
- Full Audit Trail: By capturing every change as an event, event sourcing provides a comprehensive audit trail of system activity, enabling detailed historical analysis and troubleshooting.
- Temporal Queries: Since events are stored chronologically, event-sourced systems can query past states of the application, facilitating temporal queries and temporal data analysis.
- Resilience and Recoverability: The event log serves as a reliable source of truth that can be replayed to rebuild application state in case of failures or data corruption.
- Scalability and Performance: Event sourcing enables horizontal scalability by distributing event processing across multiple nodes. It also optimizes write performance since appending events is typically append-only.
Event Sourcing Database Design Patterns
In the area of database design, event sourcing is a powerful approach for capturing and storing changes to the application state over time. In this article, We will learn about the concept of event sourcing, detailing its principles, benefits, and implementation, and providing examples to understand in detail.
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