In order to understand the benefits and reasons why event-driven architecture is so important in the world of microservices today, it's important to step back in time just a little. Of course, in software programming years, a few months could be equivalent to nearly a decade in normal time. Nevertheless, in that not-so-distant past, applications mainly worked on request-driven models where the application responded to rules-driven requests that were highly orchestrated and controlled. They were dependent on other services to a large degree. Now, dial the time machine forward to today, where decentralized microservices are in demand, and we start to see more event-driven architecture in the works. Event-driven architecture is less dependent on rules and requests and can independently respond to events in the programming environment. These differences are related to the "orchestration vs. choreography" architecture debate. They have created significant changes that go along with newer machine-driven APIs instead of traditional user-driven patterns. Understanding the ins and outs of event-driven architecture (EDA) can help decision-makers evaluate their application building needs and make smart decisions about EDA for an agile future in an unpredictable world.

What is EDA?

First of all, EDA is another of many software development and design models. As the name suggests, an EDA-based application "responds" to events that happen around it. The way it communicates, captures, and processes data and responds to its environment is not dependent upon other services or rules. The service can respond to an event independently, unimpeded by circumstances going on elsewhere in the system. By using an event-driven architecture model, an application can be created, tested, deployed, taken down, or updated quickly and easily without having much, if any, impact on other parts of the system.

How it works: example architecture

Here's an example from Amazon of an event-driven architecture for an e-commerce site. This architecture enables the site to react to changes from a variety of sources during times of peak demand, without crashing the application or over-provisioning resources.

Understanding Events in EDA

Simply put, an event in the EDA application is anything like a tap, typing text into a field, a mouse click, using a drop-down menu, sending a voice command, or some type of sensor input that the system detects as an event. Users can generate an event, or even a machine or external situation can create an event that the app might respond to. It's a state change that triggers action within the software.

Benefits of Event-Driven Architecture

The sheer volume of data and the speed with which it needs to be streamed, crunched, and analyzed has exploded in recent years, and it's not slowing down any time soon, if ever. Traditional database-driven applications struggle to manage all that data being generated, and they can easily get hobbled, which can cause severe difficulties for organizations that rely on quick, streaming data in real-time. So it's clear that developers must think about handling data differently. The reason event-driven architecture works in these heavy data streaming situations is that they are not weighed down by dependencies on other services. There are far fewer service-coupling situations that create dependencies that can slow things down. They don't have to know how other services handle the data, and they don't need to worry about it. They don't have to wait for another service to do something, they can simply respond to their specified event, move on, and process their next event quickly and efficiently. This translates into several benefits for app users.

1. Optimal Scalability

One of the biggest benefits of EDA is its scalability. Because a microservice in an EDA will typically only perform one task responding to an event, it is easy to add or subtract components and identify data bottlenecks. When a specific service isn't responding properly, you can scale just that one service, take it offline, fix it and restore it without disrupting the processes of other microservices in the EDA system. It's also possible to add more services as demand increases. EDA is scalable and responsive to business needs and demands as they change.

2. The Freedom of Being Asynchronous

Because event-based architectures work asynchronously, other microservices' actions don't block them or hinder them. They can move from one task to another task freely. As events happen, they respond and move on. They don't even have to worry about one event happening before another event. They can queue or buffer events so that users don't put too much pressure on the system, which can cause service blockages.

3. Easier Disaster Recovery

EDA can also be responsive in the event that any problems occur during the process of multiple, simultaneous data transactions. Problems can be pinpointed back to a specific event for the impacted service. By replaying past events recorded in event storage, the EDA can rollback and recover data from a previous state automatically so the user doesn't lose it. This enhances agility and resiliency in the face of unpredictable situations.

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How the Benefits of EDA Help Your Customers

The independence, scalability, agility, and resilience of EDA microservices can help you devise systems that provide incredibly competitive value to your customers. This type of application architecture keeps critical data, in huge volumes, streaming and processing through the system without the type of backups they were accustomed to in more dependent, monolithic systems. For instance:

• Customers Get Better Data Faster
• Consider the real-world example of financial institutions needing to immediately identify fraudulent transactions, as they happen, to stanch loss, protect customers, and preserve resources. The immediacy of the data is critical. Even if the data is only a few seconds old, that may still be too old to take the right action. EDA's real-time data streaming and event responsiveness can help the company isolate the misdeed and shut it down fast. On a more positive note, customers who need real-time market data in order to make quick trading decisions have access to fresh data "in the now" through an EDA system.
• Lower Bandwidth Costs and ConstraintsBecause of the loose coupling within an event-driven architecture, clients don't have to make massive upgrades or spend thousands on new hardware platforms to handle the significant improvement in data streaming. They can start using new systems without impacting the layering, which means they can simply climb aboard and enjoy a seamless transition with cost-effective, efficient operation. EDA has lightweight components that can even enable them to run on older, smaller hardware systems that clients already have. Of course, EDA is also perfect for cloud computing, saving significant bandwidth and providing other benefits in flexibility and scalability.
• Highly Scalable and Flexible Unlike a monolithic software application that can be difficult to scale without adding entirely new instances of it, EDA microservices can be scaled as needed for added flexibility. For example, an eCommerce inventory management system could have trouble dealing with increased demand without getting bombarded and hampering efficiency. With an event-driven architecture, smaller packages of code can be added as necessary. They can run on smaller systems or in private cloud containers by just adding instances of the additional service, not the entire monolithic structures of old. This empowers organizations to adapt quickly to new situations by scaling up or down whenever there is a change that they need to deal with. It makes the organization much more nimble and efficient.
• Agility to Drive SalesEDA can process and analyze so much more data in real-time, without the latency involved in older systems. Decision-makers can see and gain insight from consumer behavior and patterns quickly. Applying this data to machine learning and all of the Internet of Things (IoT) devices in a business system can instigate and enhance interactions with consumers to target them in the right moment to make sales.

Some Disadvantages of Event-Driven Architecture

For all it's petals, every great rose still has a few thorns that organizations must consider before making final decisions. In fact, it is sometimes the flip side of the advantages that bring some concerns. Earlier, we discussed how loosely-coupled services provide agility. At the same time, that loose coupling makes it hard for the system to anticipate events happening at different times. In order to make sure events trigger the right responses across the board, it's critical to spend extra time evaluating the system carefully to prevent security gaps and head off failures that could cause data loss. This can be a very complicated process as more instances of the system are scaled in.

1. Documenting the Unknown

The learning curve necessary to implement EDA can be daunting, just because it is such a significant paradigm shift from classic software development structures. In earlier days, developers strove to document every possible action and response within the system into rules and databases. Every possible outcome was cataloged within the system already. The flexibility of EDA creates uncertainty because a great deal of data streaming into the system comes from the outside and can't easily be documented, making it difficult to anticipate some outcomes.

2. Anticipating the Unforeseen

Events in the EDA system are asynchronous, which means there's no way to anticipate what order events will come in. It's hard to assure delivery of any specific outcome, which could lead to duplicates or surprise conditions that might require a response that depends on the context of the event.

3. Error Handling Problems

It can be hard to trace an event that caused a problem in this decentralized architecture. As each event is produced and subsequently consumed within the EDA, the sheer proliferation and volume of events can make a maze out of trying to track down the root of the problem and fix it. Although it can be done, of course, it's not easy. In this way, it can even reduce flexibility and take up precious time and resources unless careful planning happens first.

EDA is not a Cure-All

Just like any other type of software architecture, EDA has its high points and low points. EDA has many benefits because of how it circumscribes each process, and yet that causes a high degree of complexity for developers to process and interact with. This very fact may introduce errors in and of itself. At the same time, EDA is a great tool for boosting interconnectivity and interoperability for IoT's growing world. It's still not the correct answer for every problem, though. It must be applied correctly, and with thorough strategizing ahead of time.

Things to Consider Before Adopting Event-Driven Architecture

So, before jumping headfirst into the world of event-driven architecture, decision-makers must consider a wide range of their needs and their customers' needs so the right combination of approaches can be applied to the best advantage.

• Event Sourcing
• One way to tame some of the unpredictability of events is to have an event sourcing system. Although it can be tough to apply an amalgamation of loosely-coupled services, varying data stores, and minute transactions, event sourcing enables you to save state changes of different entities as a series of events. Although updates and deletions are not applied directly onto the data itself, there is a record of how events worked out that developers can use to track errors and isolate them.
• Discovering Event Information
• One of the major complexities that software designers need to figure out is how to track and catalog the varying services and events. How will you be able to find event details and descriptions? Why did an event occur? What or who created the event? Who is working on the service? These questions must be at the forefront of planning if an effective EDA is a goal.
• Effectively Handling Change
• Within an EDA application, events are continually being produced and consumed within ever-changing schemas. Extensive planning is required to ensure that event producers are aware of how their schema changes could impact services across the system. Events need to be documented and well-designed to minimize errors. Event consumers need to prepare code that adapts to constant change from the event producer side. It takes a lot of planning and thought, but the outcome can be worth the effort.
• Avoid too Many Events
• An increase in events means a necessary increase in complexity. This will overload developers with work and decrease the potential efficiencies that well-designed and conceptualized EDAs could achieve. Testing becomes more arduous, and errors could slip through to the user's side, causing congestion and system failures. To prevent the over-proliferation of events, think of how methods and events can be streamlined and simplified.

EDA and Microservices

These days, event-driven architecture and microservices frequently walk hand-in-hand with good results. The agility and scalability benefits are extremely attractive and are already benefiting many organizations as they deal with ever-increasing data streaming and analysis needs. Yet, the challenge of granularly updating states and publishing events remains a complex challenge for many. As time goes on, developers are devising solutions like transaction log mining, using databases as message queues, and event sourcing. The key to landing on the right architecture for your needs depends on taking a good look at your goals and how best to accomplish them.

Is EDA the Right Solution for You?

Lighting fast changes in the market of interconnected businesses, consumers, the IoT, and mobile services have catapulted event-driven architecture to the forefront of software development, and will continue to do so. EDA will continue to evolve and incorporate these elements into the next generation of service-oriented architecture because it offers great flexibility and scalability to big and small organizations. It can integrate new applications while providing real-time data analysis and immediate monitoring as events happen. This ensures that today's EDA solutions will be able to expand to meet changing long-term requirements.

The benefits of EDA, coupled with microservices, include lower adoption costs, operational efficiencies, faster time-to-market, and less need for invasive refactoring or disruption of existing application development efforts. The key is to design the system that will match your needs and optimize your strategic advantages. The big spend upfront is planning and analyzing how your organization functions today, which may be outside of the scope of possibility for some businesses.

If the benefits and difficulties of EDA have you sitting on the fence about which direction to take in your application approach, let's talk. Our expert developers can help you assess your needs and help you find the solution that will work best for your organization.

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