Axon Server matches metadata elements provided in a command or a query to tags defined on the command and client handling applications. For instance, you could tag commands with a country code and set the country code in the tags of the handler application. In this case, Axon Server will try to find a command handler with the same country code and send the command to that handler. If there are multiple applications found with a command handler for the requested command and matching tags, Axon Server will pick one based on the provided routing key. The same will happen if there are no applications found with matching tags, so commands will not fail because there are no matching tags. You can, of course, have multiple tags on an application, Axon Server will select the one with most the matching tags.