title: How can I queue messages in MQTT?
body: <p>I am using MQTT in an IoT application. For that purpose each IoT device will publish data to the IoT broker under their Topic and the processing server would subscribe to some wildcards topic to access the data. This processing server needs to save this data in database. Now the thing is that at one time, thousands or millions of devices will be publishing to the broker. If the processing server accesses the data, before it can finish processing it, it is swarmed by the next data. How can I solve it? I was hoping there could be some queue like mechanism at the client or broker side. If so, how can this be done? Or should I use some other protocol instead of MQTT?</p>