Event-Driven What?

In a universe where software eats the world*, developers are looking for new ways to keep their systems more robust and reliable than any other day. To do so, there are new design patterns are being born day after day. With the first breath of Microservices, Event-Driven architecture becomes one of those patterns.

In this article, I will try to explain what is Event-Driven architecture, where, and why we should use/not use it, and the pros and cons of it.

Let’s dive.

First of all, a little bit of story.

What is Event Driven Architecture, and what it is solving?

Now, since the software is eating the world*, the code bases became enormously big. Some guys suggested that microservice-based architectures would be easier to keep the whole thing up and since there will be more than one project (possibly even more than you projected), it will be easier for software developers to prevent customers from being affected by bad scenarios. Because now, decoupling comes into play. You can loosely couple your projects and with a little bit of precaution, your customers can use your product as a free bird, without knowing anything about what is happening in the ground.

I guess we understood that Event-Driven Architecture is related to loosely coupling your microservices with each other.

Now, to move forward, as described in the Amazon language, here is an explanation for Event-Driven Architecture.

An event-driven architecture uses events to trigger and communicate between decoupled services and is common in modern applications built with microservices. An event is a change in state, or an update, like an item being placed in a shopping cart on an e-commerce website. Events can either carry the state (the item purchased, its price, and a delivery address) or events can be identifiers (a notification that an order was shipped).

By introducing a middleman known as an event broker, event-driven architecture enables what’s called loose coupling of applications, meaning applications and devices don’t need to know where they are sending information, or where the information they’re consuming comes from.

The above example shows a very simple example of an Event-Driven Architecture of an e-commerce application. Here, we see when the order service runs, it fires an event that is feeding the Payment Service, and that payment service is communicating its related gateway to allow a person to buy the product, based on the event that is already been fired by Order Service. And after that, the payment service also fires an event, which is feeding the Shipping Service. In the beginning, the order service possibly included a userId in the event, hence shipping service will be able to ship the product to the right person. The shipping Service also communicates with Warehouse Control Service to be sure that it has the right amount of product, and after that, the shipping service also fires an event which is feeding the Notification Service, with the userId and productId, so that we will be able to send e-mail, sms and/or push notifications to the customer including invoice and/or the cargo steps.

Before moving forward, the above one is just an example, I know it might not be the right design choice for an e-commerce application. But, you got the idea anyway.

PROS and CONS

Pros:

1. Scalability: Event-driven architecture enables horizontal scalability by distributing the processing load across multiple components, allowing systems to handle high volumes of events efficiently.
2. Loose Coupling: Components in an event-driven system are loosely coupled. Changes in one component have minimal impact on others, making the system easier to maintain and evolve.
3. Real-Time Responsiveness: Event-driven systems react immediately to events, enabling real-time or near-real-time processing and decision-making. This responsiveness is beneficial for applications that require timely responses, such as financial systems or IoT environments.
4. Extensibility: New functionalities can be added by integrating new components that subscribe to relevant events, allowing the system to adapt and evolve over time without extensive modifications.

Cons:

1. Complexity: Event handling logic and coordination between components may become intricate, leading to potential event-driven race conditions and debugging challenges.
2. Event Reliability: Missed, delayed, or out-of-order events can disrupt the system’s behavior and correctness, requiring careful consideration of event durability and fault-tolerant mechanisms.
3. Event Choreography: Managing complex event flows and ensuring consistency across the system may require careful design and coordination efforts.
4. Debugging and Tracing: Tracking event flows, identifying error sources, and reproducing issues may require specialized tools and techniques for event-driven systems.

When to use Event-Driven Architecture

Here are some scenarios where EDA is particularly beneficial:

1. Real-time or near-real-time processing: Projects that require immediate or near-immediate responses to events, such as financial systems or IoT platforms, are well-suited for EDA.
2. Scalability and high event volume: By distributing event processing across multiple components, EDA enables systems to scale horizontally, accommodating increased event rates effectively.
3. Integration and interoperability: EDA provides a decoupled communication mechanism through events, allowing systems to exchange information seamlessly and facilitating interoperability between disparate systems.
4. Complex workflows and agility: The loose coupling and modularity of EDA make it easier to introduce new functionalities, adapt to changes, and evolve the system over time without significant impact on existing components.

It’s important to note that while EDA offers advantages in these scenarios, it may not be the best fit for every project. Consider the complexity, requirements, and trade-offs associated with EDA, as well as the expertise and resources available for implementing and managing an event-driven system. Assessing the specific needs of your project and evaluating the suitability of EDA in light of those needs will help determine whether to adopt an event-driven architecture.

I know, it had been a long time since you started reading this post. But hang on, the last part coming.

Here, I have prepared some questions you should ask yourself before diving into any coding, to understand if Event-Driven Architecture is a good choice for you or not.

• Does my project require real-time or near-real-time processing and responsiveness?

Consider whether your project involves time-sensitive operations or requires immediate reactions to events. EDA excels in scenarios where real-time processing and responsiveness are crucial.

• Is my project expected to handle a high volume of events or experience bursts of events?

Evaluate whether your project anticipates a significant number of events or needs to handle spikes in event traffic. EDA is beneficial for scaling horizontally and efficiently processing a large volume of events.

• Does my project involve integrating multiple systems or services?

Determine if your project requires seamless integration and communication between different systems or services. EDA provides a decoupled and flexible approach, facilitating interoperability and integration among disparate components.

• Are there any complex workflows or evolving requirements that will be in my project?

Consider whether your project involves intricate workflows or dynamic requirements that may change over time. EDA’s loose coupling and modularity allow for easier adaptation, evolution, and the addition of new functionalities without major disruptions.

• Do I have the necessary expertise and resources to design, implement, and manage an event-driven system?

Assess whether your team possesses the knowledge and skills required to successfully adopt and implement EDA. Consider the availability of tools, frameworks, and resources that support event-driven architectures.

By addressing these questions, you can gain a better understanding of whether Event-Driven Architecture aligns with the specific needs and characteristics of your project. It helps in determining whether EDA will bring the desired benefits and suit your team’s capabilities and resources.