@lyrium for Sidekiq there is, if you go to Preferences->Administration and the value under 'backlogged jobs' is at zero most of the time, you are not close to hitting the Sidekiq limit.
For Web, if at peak hours you refresh your browser and notice a slower reload, then you are close to limit.
I know this is not very scientific but it really depends on the users usage and what is happening in the fediverse.