I applied through a staffing agency. The process took 2 months. I interviewed at McKinsey & Company (Poznań, Greater Poland) in Feb 2016
Interview
I had a phone interview with Hays Representative. She recommended me for McK. There, I had an Excel and English tests and passing them gave me a chance to talk to region representatives (potential bosses) in the 2nd stage. Two people were evaluating my previous assignments and they gave me a large background check. I don't know whether there were any more stages of recruitment process.