Don't use the YAML provider if you have a large server. If you really want to use YAML provider, this may be a (bad) (untested) workaround, but you should use MySQL anyway, since YAML provider takes a lot of memory. To make it async, you need to pass the whole data array to another thread, which involves serializing all player data. This will be extremely laggy anyway. My approach is to write it progressively, by hacking YAML.