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.

Category Item Description
Event bus Total number of default event buses A maximum of one default event bus is allowed.
Total number of custom event buses A maximum of 10 custom event buses are allowed.
Number of event rules for an event bus A maximum of 10 event rules are allowed for an event bus.
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 operation A maximum of 3,000 queries per second (QPS) are allowed.
Event rule Event targets of an event rule
  • A maximum of five event targets are allowed for an event rule.
  • 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 rule In 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.

Event Event message
  • A single event message cannot be greater than 64 KB in size.
  • A maximum of 16 event messages can be sent at a time.
  • The maximum size of event messages that can be sent at a time is 256 KB.
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.
Schema Schema 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 versions A maximum of 1,000 schema versions are allowed.
Event stream Event 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 streams A maximum of 20 event streams are allowed.
Pattern of an event rule In 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 source Name 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.