Overview

What Is a Topic?

A topic is a collection of messages and serves as a logical access point through which publishers and subscribers interact. Each topic is identified by a unique name. The topic creator can configure topic policies to grant other users or cloud services permissions to perform specific operations on a topic, such as querying subscriptions or publishing messages.

Constraints

**Table 1** Restrictions on topics
Item	Quota	Description
Number of topics	3,000	If the number of topics exceeds the quota, no more topics can be created.
Topic name	1 to 255 characters	If you enter 256 or more characters, the topic cannot be created.
Display name	192 bytes	If you enter 193 or more bytes, the topic cannot be created.
Tag	20	If you add 21 or more tags to a topic, the topic cannot be created.
Tag key length	128 characters	If you enter 129 or more characters, the tag cannot be created.
Tag value length	255 characters	If you enter 256 or more characters, the tag cannot be created.
Text message title	512 bytes	None
Text message content	256 KB	The maximum length of an SMS message is 490 characters, or the message may be intercepted. Messages sent to SMS endpoints cannot contain square brackets ([]).
JSON message content	256 KB	None
Template message content	256 KB	None