By default, Channels does not offer any message history functionality. However, it is easy to implement your own message history solution - see How do I implement message (event) history?
You can also opt in to use Cache Channels. Cache channels stores the last event sent to the channel - this event is stored for a maximum of 30 minutes or until a new event arrives.
Cache Channels also supports encryption so you can ensure any data that is cached is encrypted using your own cipher and is cannot be unencrypted.
If you do no opt to use Cache Channels then no part of an event sent via Channels is stored: this includes the channel name, event name and event data.
Where Does Cache Channels Store My Data?
Cache channels only store data in memory, there is no writing to disk. As such, all cache channel data is stored in the Channels cluster of the app. Clusters are selected upon app creation and you can review available clusters in our documentation.