Introducing enhanced custom event buses in Amazon EventBridge for enterprise-scale event-driven applications

Organizations building event-driven applications on Amazon EventBridge typically start with a single custom event bus in one account. This works well when a single team owns the architecture. As adoption grows across the organization, though, things get complicated. AWS best practices recommend a multi-account structure, which means each team runs in its own account. To route events between them, teams create multiple event buses connected through cross-account rules or bus-to-bus configurations. This workaround reintroduces the operational complexity that serverless architectures are meant to eliminate. Platform teams lose visibility into who is subscribing to which events, cross-account and bus-to-bus routing charges compound quickly, and teams that need capabilities like event ordering are forced to build complex workarounds or adopt entirely different technologies.

Today, we are announcing an enhanced custom event bus in Amazon EventBridge, purpose-built for organizations scaling event-driven applications across teams and accounts. With the new enhanced custom event bus, you can deploy a single, centralized event bus shared across all AWS accounts in your organization, with ordering guarantees, a simplified Subscriber resource, and a new pricing model that delivers improved economics at scale and cost allocation for publishers and subscribers.

Let’s try it out
To get started with an enhanced custom event bus, I navigated to the EventBridge console in the AWS Management Console and opened the Create custom event bus page. I selected Custom event bus, the recommended option labeled New. The page also offered Custom event bus – classic, which continues to receive events and route them with rules and targets. Below the selection, EventBridge showed how the new bus works. One shared bus serves every team in the organization. Publishers send events, subscribers consume only what they need, and EventBridge handles ordering, retention, routing, and delivery.

The Create custom event bus page. Custom event bus is the recommended new option, with ordered delivery, filter patterns, event replay, and sharing across your AWS organization. Custom event bus – classic remains available for existing workloads.

Next, I configured resource sharing. I turned on Enable event bus sharing and selected Allow sharing only within your organization. I chose AWS account ID as the principal type. I could also share with an organization, an organizational unit, or an AWS Identity and Access Management (IAM) role or user. Sharing uses AWS Resource Access Manager (AWS RAM), so I did not have to set up cross-account permissions or bus-to-bus routing myself.

Resource sharing on the new custom event bus. I enabled sharing within my organization through AWS RAM and selected an AWS account as the principal, which is how teams publish and subscribe on the same bus without extra routing.

Organization-wide sharing
With the new enhanced custom event bus, you can create a single event bus and share it across all AWS accounts in your organization. Platform teams deploy one bus and establish it as the central event backbone, eliminating the need to configure cross-account permissions or bus-to-bus routing. Application teams across your organization can publish and subscribe to events on the same bus without waiting for infrastructure provisioning.

Publishers send events without needing to know which teams consume them, and subscribers create their own Subscriptions independently. Platform teams maintain visibility into all event flows and fine-grained control over who can publish and consume events. The new enhanced custom event bus has a default quota of 10,000 Subscribers per bus, and you can request a higher quota. That reduces the fragmentation that occurs when subscriber limits force you to split across multiple buses.

Event ordering
Event-driven architectures work best when consumers are designed around asynchronous patterns, where the order of events does not matter. There are a few cases where order does matter. In a logistics application, driver location updates must arrive in sequence. Out-of-sequence events cause routing algorithms to make decisions based on stale data.

The enhanced custom event bus supports both patterns on the same bus. Publishers can include an EventGroupId when sending events. EventBridge delivers events that share the same EventGroupId in sequence to Subscribers that chose ordered delivery. Other subscribers on that bus can receive the same events without ordering. You can keep events for each driver in the correct order without building complex workarounds, while the rest of your consumers stay fully asynchronous.

To support ordered processing, the enhanced custom event bus includes synchronous invocation for targets like AWS Lambda. Synchronous mode confirms successful processing before acknowledging the event, eliminating the common pattern of placing Amazon Simple Queue Service (Amazon SQS) between an event bus and Lambda to ensure reliability.

Subscriptions
The enhanced custom event bus introduces the Subscriber resource, which combines event filtering, target configuration, retry policies, and dead-letter destinations into a single, manageable unit. Today, achieving the same outcome with EventBridge requires configuring separate rules, targets, and retry settings across multiple resources. Subscribers simplify this by giving each consumer one resource that defines what events they want, where to deliver them, and how to handle failures.

Subscribers also include variable start time options, making it easier for teams to onboard new consumers or replay events to recover from application errors or hydrate new applications.

Event evaluation
Publishers can turn on content-based deduplication so EventBridge detects and drops retries of the same event from the payload itself. You do not have to generate and track a deduplication ID when a timeout or a partial failure sends the same event twice. EventBridge hashes the meaningful parts of the event and collapses matches that arrive within five minutes, which gives those retries exactly-once delivery semantics instead of EventBridge’s usual at-least-once model. If you already stamp your own idempotency token, keep using it. Content-based deduplication is for sources that cannot reliably identify the same event on a retry.

Subscribers can use JSONata expressions to reshape an event before it reaches a target, extracting fields, renaming them, or computing new values when a downstream API expects a different shape. If you already produce Apache Avro or Protocol Buffers events, EventBridge can deserialize those payloads to JSON, allowing subscribers fine grained filtering and routing on the full event payload without having to consume, deserialize, and match or discard on their own.

New pricing model
The enhanced custom event bus uses a new ingress and egress throughput pricing model. Publishers pay for events ingested, and subscribers pay for events delivered. This replaces the per-event model where cross-account and bus-to-bus routing charges compound in multi-bus architectures. For pricing details, visit the EventBridge pricing page.

Existing EventBridge custom event buses continue to work as they do today with no changes required. They now appear as Custom event bus – classic. The enhanced custom event bus is a new resource that you adopt at your own pace. In the console, it appears as Custom event bus.

Now available
The enhanced custom event bus is available today in the US East (N. Virginia, Ohio), US West (Oregon), Europe (Ireland, Frankfurt, Stockholm, Spain), and Asia Pacific (Hong Kong, Malaysia, Mumbai, Singapore, Sydney, Thailand, Tokyo) Regions. You can create your first enhanced custom event bus through the AWS Management Console, AWS Command Line Interface (AWS CLI), or EventBridge APIs. To get started, visit the EventBridge documentation or try it out directly in the EventBridge console.