Had no evidence of this problem on any Yosemite release thru 10.10.5 on 2011 Mac mini with third-party SSD and 8GB RAM. With El Capitan 10.11.4, the Open with on the contextual menu would lag with a Fetching… , and this seems to be a stale Launch Services database, which is fixable.
On slower hardware (read Apple internal, non-SSD drives), and initial OS X startup, there are a boatload of System services that run including Software Update, and Spotlight indexing (not only your hard drive, but the Time Machine disk too). These start up processes will cause interactive lag for a few minutes due to resource contention.
If you are attempting to run OS X on a 2GB RAM machine, it will crawl, all of the time. Not enough memory, and it is swapping (read dog slow).
Anyone knowingly, or unknowingly running anti-virus, security, or so called Mac cleaner applications will have operational issues with their Mac because these worthless, third-party utilities will interfere with the normal operation of OS X.
Some malware will also cause operational anomalies with OS X.