When teams begin deploying event-driven applications using Amazon EventBridge, a single custom event bus typically suffices. The model breaks down as adoption spreads across an organization, particularly when AWS best practices dictate separate accounts for each team. Routing events between accounts has required teams to build multiple event buses connected via cross-account rules or bus-to-bus configurations—a pattern that reintroduces the operational overhead that serverless design aims to eliminate. Platform teams struggle to track event subscriptions, routing charges accumulate across accounts and buses, and teams needing event ordering must resort to workarounds or abandon EventBridge entirely.
AWS is introducing an enhanced custom event bus built specifically for organizations scaling event-driven applications across teams and accounts. The new offering provides a single, centralized event bus deployable across all AWS accounts in an organization, complete with ordering guarantees, a simplified Subscriber resource, and a revised pricing structure that improves unit economics at scale while enabling cost allocation between publishers and subscribers.
Organization-wide sharing
The enhanced custom event bus allows creation of a single event bus shared across all AWS accounts in an organization. Platform teams can deploy one bus and establish it as the central event backbone, eliminating the need to configure cross-account permissions or bus-to-bus routing manually. Application teams across the 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 enhanced custom event bus has a default quota of 10,000 Subscribers per bus, with the option to request higher limits. This reduces the fragmentation that occurs when subscriber limits force splitting across multiple buses.
Resource sharing uses AWS Resource Access Manager (AWS RAM), eliminating the need to set up cross-account permissions or bus-to-bus routing manually. Teams can share the bus within their organization, with specific organizational units, or with particular IAM roles or users.
Event ordering
Event-driven architectures typically function best when consumers embrace asynchronous patterns where event sequence is irrelevant. However, certain use cases demand strict ordering. In logistics applications, driver location updates must arrive sequentially; out-of-order events cause routing algorithms to make decisions based on outdated information.
The enhanced custom event bus supports both patterns on the same bus. Publishers can include an EventGroupId when sending events. EventBridge delivers events sharing the same EventGroupId in sequence to Subscribers that selected ordered delivery. Other subscribers on that bus can receive the same events without ordering constraints. This allows keeping driver location events in the correct order without building complex workarounds, while the rest of consumers remain 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. Achieving the same outcome with EventBridge previously required 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 enable content-based deduplication so EventBridge detects and drops retries of the same event based on the payload itself. Teams do not need to generate and track a deduplication ID when a timeout or partial failure sends the same event twice. EventBridge hashes the meaningful parts of the event and collapses matches that arrive within five minutes, providing exactly-once delivery semantics instead of EventBridge's usual at-least-once model. Teams already using their own idempotency tokens can continue doing so; content-based deduplication targets 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. For teams already producing 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. Pricing details are available on the EventBridge pricing page.
Availability and migration
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 organizations can adopt at their own pace.
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. Teams can create their first enhanced custom event bus through the AWS Management Console, AWS Command Line Interface (AWS CLI), or EventBridge APIs.