Event-Driven Services in the Cloud: Azure Event Grid, AWS Event Bridge, and Google EventArc

I mentioned Azure Event Grid in a scenario with D365FO Business Events in a previous blog post. It is a Platform as a Service (PaaS) capability in Azure or eventing platform or event bus (I see various terms describing the service) allowing you to centrally manage events. In addition, it supports direct event filtering based on event type, prefix, or suffix, so your application will only receive events that are relevant to it.

Whether you want to handle built-in Azure events, such as a file being added to storage, or create your own custom events and event handlers, Event Grid supports both options via the same underlying model. Thus, regardless of the service or use case, intelligent routing and filtering capabilities apply to every event scenario and ensure that your apps focus on core business logic rather than worrying about event routing.

In this blog post, I like to dive into Azure Event Grid and competitive offering on the two other big cloud providers, AWS and Google.

Azure Event Grid

In 2017 Microsoft introduced Azure Event Grid as a fully-managed event routing service and the first of its kind (meaning the public cloud claimed it was the first offering the service). Dan Rosanova, previously Principal Program Manager Lead at Microsoft, now Director Program Management at Confluent, said in an InfoQ news item on the introduction:

Azure Event Grid fills a gap in the current cloud messaging space, not just in Azure but also across all cloud providers. We have services for messaging, queuing, and telemetry, but nothing for comprehensive eventing, particularly for cross-service or cross-cloud scenarios.

Within Azure service supporting Event Grid generates events routed to several event handlers. These handlers support event filtering and reliable delivery, ranging from Azure Functions to webhooks. Furthermore, underhood, the service relies on Service Fabric and thus can scale automatically to handle millions of events per second.

Event Grid model of sources and handlers

Source: https://docs.microsoft.com/en-us/azure/event-grid/overview

The Event Grid concept revolves around events emitted from a source (publisher), an Azure service, or a third-party source that adheres to the event schema (proprietary schema or the CNCF Cloud Events schema). For example, IoT Hub, Storage, and others are all event publishers in Azure. Following that, the events are sent to a topic in Event Grid, and each topic can have one or more subscribers (event handlers). A topic can be set up with the event publisher, or it can be a custom topic for custom events. Finally, event handlers respond to and process the events. Functions, WebHooks, and Event Hubs are examples of event handlers in Azure.

Azure Event Grid generally became available (GA) in February 2018 and Clemens Vasters, Principal Architect Messaging Services at Microsoft, said:

Event Grid is catching everyone’s attention because it unlocks new architectural possibilities for cloud platforms and applications: it’s the glue that enables information flow between services, and Event Grid allows expanding the capabilities of existing services by extension.

And that’s what also triggered or got the attention of AWS as they released EventBridge in July 2019, labeled as a serverless event bus that allows AWS services, Software-as-a-Service (SaaS), and custom applications to communicate with each other using events.

Since the GA, Azure EventGrid received several updates, including advanced filtering, retry policies, and support for CloudEvents. More details and samples are available on the Microsoft documentation and GitHub. Note that there is also an introductory paper available on Azure Event Grid and GitHub from Clemens.

AWS Eventbridge

You can use EventBridge to build and manage event-driven solutions by centrally controlling event ingestion, delivery, security, authorization, and error handling. Furthermore, you do not have to manage any infrastructure or scaling and only pay for the events that their applications consume, similar to Azure Event Grid. Moreover, the concepts are the same too.

How Amazon EventBridge connects applications using events

Source: https://aws.amazon.com/eventbridge/

However, Amazon Eventbridge surpasses Azure Event Grid with features (as you can see from the diagram above). It has a schema registry allowing you to discover, create, and manage OpenAPI schemas for events on EventBridge. According to the documentation, you can find schemas for existing AWS services, create and upload custom schemas, or generate a schema based on events located on an event bus. Furthermore, EventBridge enables you to generate and download code bindings for all event schemas to help quickly build applications that use those events.

Next to the schema registry, the service integrates easily with third-party services like Zendesk, Pagerduty, and SignalFx. Amazon has set up an extensive partner program for these integrations. Event Grid supports partner events (still preview) yet only has one with Auth0.  

Another capability Amazon EventBridge offers is event replay and archive –  allowing you to archive events so that you can easily replay them later by starting an event replay. Again, a capability that is not available in Azure Event Grid. Although it is something, you can find in Azure Event Hubs. You can configure the archive capability with the actions menu on the EventBridge Console and set the events’ retention period (ranging from zero days to infinite). Subsequently, you can optionally set a pattern matching filter for which events to archive. Later, when events run through the event bus, you can replay the events by selecting the appropriate archive.

Sample Implementation AWS EventBridge

Since the inception of Event Grid, I followed its evolution and wrote and presented on it. Moreover, I followed its competitive solution on AWS and, next to writing about it on InfoQ, built a simple demo around it using .NET in combination with AWS EventBridge. Below you will find a diagram of the demo I created.

Amazon EventBridge Demo

From .NET code, I send an event to a custom event bus containing a rule to send the event to a destination, an Amazon Simple Queue. Subsequently, an AWS Lambda function can poll the queue and receive the message – below shows the steps until the SQS queue.

EventBridge Demo Steps

You can find a live demo on YouTube with demoing the above (minute 19). Furthermore, you can look at other samples like in the AWS documentation or on GitHub.

Google Eventarc

With Azure and AWS offering a service to centrally manage events, Google followed in October 2020 with Eventarc to provide customers with a service to connect Cloud Run services with events from various sources, adhering to the CloudEvents standard. It became generally available in January 2021.

Eventarc’s underlying delivery mechanism is Pub/Sub, which includes topics and subscriptions similar to previously discussed Event Grid and EventBridge. Event sources create events and publish them in any format on the Pub/Sub topic. The events are then delivered to the Google Run sinks. For applications running on Cloud Run, you can use Eventarc to use a Cloud Storage event (via Cloud Audit Logs) to trigger a data processing pipeline or an event from custom sources (publishing to Cloud Pub/Sub) to signal between microservices.

Eventarc Overview

Source: https://codelabs.developers.google.com/codelabs/cloud-run-events#1

The diagram above shows what Google hopes to achieve with Eventarc. Currently, you can Cloud Run Service as a destination, and recently Cloud Run for Anthos has been added. Additionally, you can leverage a UI through the Google Cloud console allowing you to view, edit, and delete EventArc triggers. Lastly, you can find more details and samples on GitHub.

CloudEvents Schema

Before I end the blog post with some conclusions, I like to discuss the CloudEvent schema. CloudEvents is an open-source specification for consistently describing event data to make event declaration and delivery easier across services, platforms, and beyond. The Cloud Native Computing Foundation (CNCF) is the driving force behind the specification, which reached the version 1.0 milestone in October 2019.

Clemens Vasters, Principal Architect Messaging Services at Microsoft, stated in an InfoQ news item on CloudEvents:

The goal was to provide an industry definition and open framework for what an “event” is, what its minimal semantic elements are, and how events are encoded for transfer and how they are transferred and do so using the major encodings and application protocols in use today rather than inventing new ones.

Earlier I mentioned that Azure Event Grid has its own proprietary schema and supports CloudEvent schema. The differences are shown below:

CloudEvent vs Event Grid Schema

Note that Azure Event Grid and Google Eventarc support the CloudEvent schema; however, AWS EventBridge does not, leading to customization.


From this blog post, you can probably conclude that AWS with Eventbridge delivers the most complete event bus or eventing platform in the cloud than Event Grid and Eventarc. If I rank each, AWS comes first, Azure second, and Eventarc third based on features and maturity. The service overlap in concepts, yet implementation, support, and features differ dramatically. Interestingly, they all support changes in their respective storage service. Azure Event Grid brings support for events like when blobs are created, and EventBridge supports S3 notifications and Eventarc triggers for Cloud storage. You can think of various scenarios regarding storage and events, for instance, the pipe and filters pattern implementation discussed in my first blog post.

A High-Level View of Cloud Governance

Something that intrigues me in the cloud is governance. As a technical integration architect, that’s the role/function I have in my current day-to-day job. Yet, during designing solutions, I usually do not think about it or talk to a customer set on moving to the cloud – that’s a cloud migration process, which I am generally not involved with. Still, it should have my attention, and it has now.

You might ask if it sounds unfamiliar to you, what is governance? First, you could look up the term in Wikipedia. And you’ll find the explanation or definition in the first lines mentioning a process of interactions through laws, norms, power, or language of an organized society over a social system such as tribe, family, formal or informal organization. Yet how does this relate to the cloud? Well, very simple, it is still a process of interactions, however, defined by what a cloud provider deems necessary to keep costs, access to data, consistency, and deployments under control.

A Cloud provider like Microsoft, AWS, and Google can provide you with guidance regarding governance to manage costs, secure resources and access to data, and consistency in the deployment of resources – each provides frameworks for that:

The Google Adoption Framework whitepaper will mention governance regarding data, cost control, security, and cloud resources management. While AWS CAF has governance as one of its six perspectives. And Microsoft has a section of Govern in their Framework and a landing page.

Microsoft Cloud Adoption Framework

Source: https://docs.microsoft.com/en-us/azure/cloud-adoption-framework/overview

I now like to zoom further into governance on Microsoft Azure since I predominantly work as a (solution) architect (integration) on that Cloud platform. Furthermore, I will not look at the process extensively described in the CAF, yet more on some of the services and capabilities available in Azure and add some of my views and relevant resources I found.

Azure Resources

Microsoft provides policies on Azure to allow you to keep resources compliant. When a policy is assigned, it will, when it is triggered, evaluate if it adheres to a definition. You can use these policies to implement governance for resource consistency, regulatory compliance, security, cost, and management. For more details on Azure Policies, see Azure Policy on GitHub.

Next to policies tagging is another aspect of governance in Azure or any cloud platform. With tags, you can assign helpful information to any resource within your cloud infrastructure – usually information not included in the name of available in the overview of the resource. Tagging is critical for cost management, operations, and management of resources. More details on how to apply them are available in the decision guide.

If you work at a company with many subscriptions, or the customer you work for does, you can leverage management groups –a level of scope above subscriptions. It provides a way to organize subscriptions into containers and thus provide a logical structure. Moreover, you can apply specific governance conditions with management groups as each subscription in a group inherits them.

Diagram of a sample management group hierarchy.

Source: https://docs.microsoft.com/en-us/azure/governance/management-groups/overview

More details on management groups are available on the GitHub page.

Another intriguing service is the Azure Resource Graph, a capability in Azure to query, explore, and analyze your cloud resources. It includes an Explorer you can use in the Azure portal and can also be used programmatically through the Azure CLI, Azure PowerShell and Azure SDK for .NET.

You can use Graph Explorer to explore resources based on your governance requirements and assess the impact of applying policies in your environments. The query language is based on the Kusto query language used by Azure Data Explorer. More details are available on the GitHub page.

And lastly, Azure Blueprints can enable you to define a repeatable set of Azure resources that implements and adheres to an organization’s standards, patterns, and requirements. As a result, you can orchestrate the deployment of various resource templates and other artifacts such as the earlier mentioned policies, role assignments, ARM templates, and resource groups in a declarative way. With blueprints, you can consistently deploy predefined environments. Other public cloud providers offer blueprints as well: AWS Blueprints and GCP Blueprints. You can find more details on Azure blueprints on GitHub.

Cost Management

The cost management + billing service and features are available in any subscription in the Azure portal. It will allow you to do administrative tasks around billing, set spending thresholds, and proactively analyze azure cost generation. A key aspect is regarding cost control is to set up budgets at the beginning once a subscription before workloads land or resources are provisioned for the development of cloud solutions. Furthermore, once consumption of Azure resources starts, you can look at recommendations for cost optimizations. Moreover, Azure Advisor can help identify underutilized or unused resources to be optimized or shut down.

Example of the Subscription Overview tab showing Offer and Offer ID

Source: https://docs.microsoft.com/en-us/azure/cost-management-billing/costs/understand-cost-mgt-data


An essential aspect of governance is security, for example, who gets access to what resource in Azure. A consistent way to set that up is by applying the earlier mentioned blueprint. Azure AD plays a role as well when you add accounts, service principles (an identity created for use with applications, hosted services, and automated tools to access Azure resources – similar to a service account on Windows), and app registrations (Application Object).

Azure AD is an Identity and Access solution with several features, such as conditional access, Multi-Factor Authentication (MFA), and Singel-SignOn (SSO) support. In addition, it is an essential service with regards to governance to provide access to the application (services) and people to Azure resources – and you want that consistent and accurate when it comes to who is responsible for what. And lastly, Microsoft provides best practices and guidance on this service you can look into.

Data Governance

Microsoft launched Purview into a public preview for data governance in December 2020, and it became generally available later in October 2021. With Azure Purview, the company delivers an Azure service that can help you understand what data your company has and provide means to manage the data’s compliance with privacy regulations and derive valuable insights.