This topic describes the limits of EventBridge. To prevent application exceptions, do not exceed the limits when you use EventBridge.

The following table describes the limits of EventBridge.

CategoryItemDescription
Event busTotal number of system event busesA maximum of one system event bus is allowed.
Total number of custom event busesA maximum of 50 custom event buses are allowed.
Number of event rules for an event busA maximum of 50 event rules are allowed.
Name of an event bus
  • The name can be up to 127 characters in length. It must start with a letter or a digit, and can contain letters, digits, and hyphens (-).
  • The reserved keyword "default" cannot be used as the name of an event bus.
  • The name cannot be a string that is prefixed with eventbridge-reserved-.
Frequency of calling the PutEvents API operationA maximum of 3,000 queries per second (QPS) are allowed for each bus.
Event ruleEvent targets of an event rule
  • A maximum of five event targets are allowed.
  • An event target must reside in the region where EventBridge is activated.
  • An event target must be a service instance in your Alibaba Cloud account.
  • The ID of an event target must be unique.
Pattern of an event ruleIn the stringExpression pattern, each field can contain up to five expressions in the map data structure.
Name of an event rule
  • The name can be up to 127 characters in length. It must start with a letter or a digit, and can contain letters, digits, and hyphens (-).
  • The name cannot be a string that is prefixed with eventbridge-reserved-.
Transformation of the event content
  • template: Its value can be up to 10,240 characters in length.

  • value: Its value can be up to 1,024 characters in length.

EventEvent message
  • An event message cannot exceed 256 KB in size.
  • A maximum of 16 event messages can be sent at a time.
  • The total size of event messages that are sent in a batch cannot exceed 1 MB.
Event field
  • id: Its value can be up to 128 characters in length. It must start with a letter or a digit, and can contain letters, digits, and hyphens (-).
  • source: Its value can be up to 128 characters in length.
  • subject: Its value can be up to 512 characters in length.
  • type: Its value can be up to 64 characters in length.
SchemaSchema name
  • The name can contain only letters, digits, hyphens (-), underscores (_), and periods (.).
  • The name can be up to 128 characters in length. If the name that you specify is more than 128 characters in length, excess characters are deleted.
Number of schema versionsA maximum of 1,000 schema versions are allowed.
Event streamEvent stream name
  • The name must start with a letter or a digit, and can contain letters, digits, and hyphens (-).
  • The name can be up to 127 characters in length. If the name that you specify is more than 127 characters in length, excess characters are deleted.
Number of event streamsA maximum of 50 event streams are allowed.
Pattern of an event ruleIn the stringExpression pattern, each field can contain up to five expressions in the map data structure.
Transformation of the event content
  • template: Its value can be up to 10,240 characters in length.

  • value: Its value can be up to 1,024 characters in length.

Event sourceName of an event source
  • The name can contain letters, digits, hyphens (-), and periods (.).
  • The name can be up to 127 characters in length. If the name that you specify is more than 127 characters in length, excess characters are deleted.
Note The number of event buses, event rules, and event streams in the preceding table are limits for a single region.