The enhanced Custom Event Bus is intended for organizations that use multiple AWS accounts to isolate teams and applications but find that event routing becomes complex and costly as the number of consumers grows. AWS's new model positions a central bus as an organizational event backbone, shared across accounts via AWS Resource Access Manager (RAM). According to AWS, the bus supports up to 10,000 subscribers by default, with the option to request a higher quota.
This changes both the governance and technical models. A platform team can establish a central bus while allowing application teams to publish and subscribe from their own accounts. Rather than configuring every cross-account connection, the platform team sets boundaries around the bus, and individual application teams manage their own subscriptions, filtering, targets, retries, and failure destinations. AWS says this creates a separation between platform-level governance and application-level event consumption, potentially reducing infrastructure work for onboarding new consumers.
The update also introduces synchronous invocation for targets such as AWS Lambda, removing the need for an intermediate Amazon SQS queue just to provide stronger processing acknowledgement. This enables the bus to support both conventional asynchronous event consumption and workloads where ordering and processing confirmation are important. The new Subscriber resource simplifies how consumers are represented in the EventBridge model, replacing combinations of rules and targets.