In the discourse root directory, there’s a bin folder. There are a few files identical to the commands we use on a daily basis i.e. rake, rails etc.
Its recommended to use them instead of bundle exec due to performance and utility reasons.
Example:
We’ve been facing issues with running tests and we usually remove the poll plugin to get rid of them. The cause of this was that the migrations of poll plugin hadn’t run.
Had we used bin/rake instead of bundle exec rake, it would have automagically set LOAD_PLUGINS=1.
You can read up the magic by opening the files and seeing for yourself if you don’t believe me. 
Discussion:
https://meta.discourse.org/t/rake-db-migrate-should-load-plugins-by-default/167151/5