Even Driven Architecture

Event-driven architecture (EDA) is a popular architectural pattern that enables the creation of highly scalable and responsive systems. It has gained significant popularity in recent years as organizations move towards microservices and serverless computing. In this article, we will discuss how event-driven architecture can be used to create most of the asynchronous integration.

When to use event-driven architecture?

Event-driven architecture is an ideal solution for building applications that have a large number of components or services that need to communicate with each other asynchronously. It's particularly useful when dealing with complex business processes that require near real-time data processing and immediate action. EDA allows for loosely coupled components, which means that each component can operate independently of the others, making it easier to scale the system horizontally.

When not to use this pattern?

However, event-driven architecture is not always the best solution for every application. If you are building an application that requires sequential processing or has a small number of components that communicate with each other, then EDA may be overkill. Additionally, if you are building an application that requires strict data consistency, you may need to look for other options.

Required component

In an event-driven architecture, the components of the system are connected through a messaging system, which is responsible for transporting events between components. The messaging system should be able to handle a large number of messages, with the ability to scale horizontally as the system grows. This means that the messaging system should be highly available, reliable, and performant.

One of the critical integration components required for event-driven architecture is an event broker. An event broker is responsible for receiving events from producers, storing them temporarily, and then forwarding them to consumers. An event broker should be able to support multiple producers and consumers, guarantee message delivery, and provide message persistence. Some popular event brokers include Apache Kafka, AWS Kinesis, and RabbitMQ.

Event-Driven Architecture vs API-First (aka API-Led)

Event-driven architecture (EDA) and API-first are two distinct approaches to building software systems, each with its own advantages and use cases. Event-driven architecture is a style of software architecture where components communicate with each other through events. An event is a notification that something has happened, and components can react to events in real-time. EDA provides a flexible and scalable approach to building complex systems that require real-time processing and immediate action. EDA is particularly useful for integrating microservices and serverless computing, as it provides a natural way of integrating these services through messaging and event-driven communication.

API-first, on the other hand, is an approach to building software systems that focuses on designing the API first, before any implementation is done. The API is designed to be easy to use, scalable, and maintainable, and it is used as a contract between the client and server. API-first provides a way to ensure that the API is designed to meet the needs of the client and to prevent breaking changes in the future.

In general, EDA is better suited for systems that require real-time processing and immediate action, while API-first is better suited for systems that require a stable and scalable API. EDA provides a way to react to events in real-time, while API-first provides a stable and maintainable API that can be used by clients to access the system's functionality. Ultimately, the choice between EDA and API-first depends on the specific requirements of the system being developed. Both approaches have their own benefits and drawbacks, and the choice depends on factors such as the complexity of the system, the need for real-time processing, and the requirements of the API.

The difference between a Message and an Event

In event-driven architecture, messages and events are two key concepts that play a critical role in enabling communication between different components of a system. Although the terms "message" and "event" are sometimes used interchangeably, there is a subtle difference between them.

A message is a unit of communication between two or more components of a system. It is typically used to transfer data or trigger an action. A message can be synchronous or asynchronous, and it is often sent through a message broker or other messaging system. On the other hand, an event is a notification that something has happened within a system. An event can be triggered by a user action, a system event, or an external event. Unlike a message, an event is typically not directed at any specific component of the system. Instead, it is broadcast to all interested components, which can then take appropriate action based on the event.

In other words, while a message is sent to a specific recipient, an event is broadcast to all interested parties. Additionally, an event typically carries less information than a message and is focused on notifying other components of a change in state or a significant occurrence within the system. Understanding the difference between messages and events is important when designing an event-driven architecture. By using events to trigger actions within the system, components can react to changes in state in real time, leading to more efficient and responsive systems.

Type of event-driven architecture

There are several types of event-driven architecture (EDA) patterns that can be used to structure the communication between components in an event-driven system. Martin Fowler, a software developer and author, has identified four primary patterns:

Event Notification: In this pattern, components notify other components of changes by broadcasting events. Each component interested in a particular event subscribes to it, and the component that generated the event sends it to all subscribers.
Event-carried state transfer: This pattern is used when one component needs to retrieve data from another component. Instead of making a direct request for data, the component sends a request event to the other component, which then responds with a data event.
Event Sourcing: In this pattern, the state of the system is represented as a sequence of events. Each event represents a change in the system's state, and the current state of the system is derived from the events.
Command Query Responsibility Segregation (CQRS): CQRS is a pattern that separates the read and write operations of a system into separate components. The write component updates the state of the system by generating events, while the read component retrieves data from the events generated by the write component.

Each of these patterns provides a different way of structuring the communication between components in an event-driven system. The choice of pattern depends on the specific requirements of the system being developed.