Leaderboards refresh at specific intervals - 12 hours across all categories. You can check the next refresh time on top of the leaderboards header.
Your profile, for example https://fortnitedb.com/v2/en/profile/FortniteDB Kav comes with another timer that you can see above your loadout. Considering this scenario, your profile can be fetched ( to my database ) in 9 hours and 31 minutes, the leaderboards will refresh in 11 hours and 55 minutes. So once you "fetch you profile" by simply accessing the page, before the leaderboards refresh your leaderboards data will be updated if eligible.