By storing topics and messages in buffers and accessing them using buffer IDs, you can exchange MQTT messages more efficiently. You can use a total of four buffers (with IDs 0 to 3) for topic buffers and message buffers, respectively.
AT+MBT=<Topic Buffer ID>,"<Topic>"
at+mbt=0,"test/test_topic_0"
OK
at+mbt=1,"test/test_topic_1"
OK
at+mbt=2,"test/test_topic_2"
OK
at+mbt=3,"test/test_topic_3"
OK
AT+MBM=<Message Buffer ID>,"<Message>"
at+mbm=0,"message 0"
OK
at+mbm=1,"message 1"
OK
at+mbm=2,"message 2"
OK
at+mbm=3,"message 3"
OK