Why AWS EventBridge changes everything..

“Events, dear boy, events”

Harold McMillan

[tl;dr AWS EventBridge may encourage SaaS businesses to formally define and manage public event models that other businesses can design into their workflows. In turn, this may enable businesses to achieve agility goals by decomposing their organizations into smaller, event-driven “cells” with workflows empowered by multiple SaaS capabilities.]

Last week, Amazon formally announced the launch of the AWS EventBridge service. What makes this announcement so special?

The biggest single technical benefit is the avoidance of the need for webhooks or polling APIs. (See here for a good explanation of the difference.)

Webhooks are generally not considered a scalable solution for SaaS services, as significant engineering is required to make it robust, and consuming applications need to be designed to handle web-hook API calls.

HTTP-based APIs exposed by 3rd party services can be polled by applications that need to know if state has changed, but this polling consumes resources even when nothing changes. Again, this has scalability issues on both the SaaS provider as well as the application consumer.

In both cases, the principle metaphor connecting both the SaaS and consuming application is the ‘service interface’ abstraction – i.e., executing an operation on a resource. As such, this is a technical solution to a technical problem.

From APIs to Events

While this ‘service-based’ model of distributed programming is extremely powerful, it is not an appropriate abstraction for connecting behaviors across multiple services in a value chain. To align with business-level concepts such as Business Process Modelling, event-driven architectures are becoming more and more popular to model complex workflows both within and between organizations.

This trend is accelerated by the desire of organizations to become more “agile”. Increasingly organizations are recognizing this must manifest itself as breaking down the organization into more manageable, semi-autonomous “cells” (see this article from McKinsey as an example). With cells, the event metaphor fits naturally: cells can decide which events they care about, and also decide what events they in turn create that other cells may use.

3rd party service providers (i.e., SaaS companies such as SalesForce, Workday, Office365, ServiceNow, Datadog, etc) empower organizational cells and enable them to achieve far more than a small cell otherwise could. The “cell” concept cannot be fully realized unless every cell has the ability to define and control how it uses these services to achieve its own mission.

In addition, as value/supply chains become more complex, and more (3rd party or internal) providers are embedded in those workflows , the need for a more natural, adaptable way of integrating processes has become evident.

But event-driven architectures require a common ‘bus’ – a target-neutral means to allow zero or more consumers express an interest in receiving events published on the bus. This historically has been impractical to do at scale between organizations (or even within organizations) without requiring all parties to agree on a neutral 3rd party to manage the bus, and at the additional risk of creating a change bottleneck: hence the historic preference for point-to-point HTTP-based standards.

Services like the AWS EventBridge for the first time allow autonomous SaaS solutions to publish a formal event model that can be consumed programmatically and seamlessly included in local (cell-specific) workflows. In addition, this event model can be neutral to the underlying technology and cloud provider.

How it works and what makes it different

The key feature of the EventBridge is the separation of the publisher from the consumer, and the way that business rules to manage the routing and transformation of events is handled.

Once an organization (or AWS account) has registered as a consumer with the publisher (the owner of the “event source”), a logical “event bus” is created to represent all events for that org/account. The consuming org/account can then setup whatever routing and transformation rules it needs for any internal consumers of those events, without any further dependency on the publishing organization. So consumer organizations/accounts have full control over what is published internally to consuming applications.

With appropriate guard-rails in place, individual teams (“cells”) can define and configure their own routing rules, and not rely on any centralized team – a key weakness in many legacy ESB solutions.

Note that the EventBridge has predefined service limits – it has a (reasonably – 400 events/sec) high throughput, but is a high latency service (0.5sec). So low-latency use cases such as electronic trading are not, as this point, an appropriate use case for EventBridge.

The use of EventBridge for internal enterprise event handling should be considered carefully: the 100 event buses per account essentially limits the number of publishers that can be handled by any one account to 100. For most use cases, this should be more than enough, but many large organizations may have many more than 100 ‘publishers’ publishing on their ESB. If each publisher can be viewed as a part of an end-to-end business value-stream, then any value-stream with more than 100 components (i.e., unique event models) is likely to be overly complex. In practice, a ‘publisher’ is likely to be an enterprise application: therefore some significant complexity reduction and consolidation (of event models, if not actual code) would be needed to ensure such organizations can use EventBridge internally effectively.

The AWS Way (also, the Cloud Way)

It’s worth noting that key to Amazon’s success is its ability to “eat its own dogfood“. Every service in Amazon and AWS is built atop other services. No service is allowed to get so big and bloated it cannot be managed effectively. Abstractions are ‘clean’ – rather than add bells and whistles to an existing service, a new service is created which leverages the underlying service or services.

AWS has consistently required every service to have and maintain an API model, which – for asynchronous/autonomous services – leads naturally to an event model. This in turn has made it natural for AWS EventBridge to come out-of-the-box with a number of events already emitted by AWS services that can be leveraged for customer solutions. (For now, many of these events are limited to generic CloudTrail-related events – specifically tracking API calls – but in the future it’s reasonable to expect more service-specific events to be made available.)

AWS does have one key advantage over other major cloud providers such as Google GCP and Microsoft Azure: it set out to build a business (an online marketplace) using these services. So it’s strategy was (and is) driven by its vision for how to build a globally scalable online business – not by the need to provide technology services to businesses. To this extent, it’s hard to see Google and Microsoft being anything other than followers of AWS’s lead.

A Prediction..

Businesses which also follow the Amazon-inspired growth/innovation and organization model will likely have a better chance of succeeding in the digital age. And it is for these businesses that EventBridge will have the most impact – far beyond the technological improvements afforded by the use of events vs webhooks/APIs.

Consequently, as more SaaS companies are on-boarded onto the AWS EventBridge eco-system, we can expect more event models to be published. Tools for managing and evolving event models will evolve and improve so they become more accessible and useful for non-traditional IT folks (i.e., process and workflow designers) – currently the only way right now to see event model definitions seems to be by actually creating business rules.

This increased focus on SaaS integrations may (perhaps) inspire firms to re-organize their internal capabilities along similar lines, as internal service providers, empowering cells across the organization and with a published and accessible software-driven event model – noting that while events may be published and received digitally, they can still be actioned by humans for non-digital processes (e.g., complex pricing decision making, responding to help desk requests, etc).

The roster of SaaS firms signing up to EventBridge over the coming months will hopefully bear out this prediction. A good sense of what services could be onboarded can be had by looking at all the SaaS (and IoT) services integrated by IFTTT.

In the meantime, it is time to explore the re-imagined integration opportunities afforded by AWS EventBridge..

Why AWS EventBridge changes everything..

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