All listings are sorted using an algorithm unique to the preferences outlined in your individual profile. This means that based on your needs/skills, you will see listings that are more likely to be the best match for you towards the top of the search results.
That being said, you will always be able to see the user's status (i.e. whether they are online now, or have been seen 1 hour, day, or week ago) to see how active the user is on site.
Users who have been active within the past week are more likely to respond to messages as they are usually still engaged in an active search.