- Anything that doesn’t use the client<->server connection in any way. Examples:
- Independent network connections
- HTTP Web APIs (e.g REST services)
- Connections to external applications (SQL servers, web servers, a link with another application on a player’s computer, …).
- …
- Other I/O
- Saving files (not including files managed by MC/Sponge)
- Polling for the presents or absence of a file
- …
- Independent network connections
(Disclamer, I could be completely wrong, but these are things you can do in an async thread)