If you can understand what makes McKinsey interview tough, you can better prepare yourself, maximize your performance, and increase the likelihood that you'll make it to the next round or get that job offer. My understanding - from chatting with friends who have interviewed candidates for other firms - is that these factors also apply to other top-tier consulting firms like Bain and BCG.
1. You have to have a "spike"Candidates must exhibit distinctiveness (also known as a "spike")in at least one dimension - and preferably more - across the case interviews and personal experience interviews (PEI). This means it's not enough to not mess up or just do OK in all facets (also known as a "flat read" by assessors) of the interview to pass to the next round or get a job offer. Bringing your "A" game is insufficient - somewhere in your interview, you have to exhibit some "A plus" game.
2. The bar is highJust getting to a "flat read" can be tough, achieving a "spike" is even harder and it's not just enough to perform well relative to the other candidates. There are objective criteria in a scoring rubric that must be met in order to get a passing and distinctive scores. So, even if you're the best of the batch on a particular day, you still won't get a pass or job offer unless your performance clears a high, standardized bar.
3. Preparation can only take you so farCase prep can certainly improve your performance, but it's not a skill that you can master. There's always a chance that a case will go deep in an area where you're weak or haven't prepared. And it's rare that a case will perfectly fit a framework you've learned or memorized. Case interviews are not about what facts or frameworks you know - they are about how you think through, approach, and break down a problem. So you have to be broad, thorough, and flexible in your study and preparation and during the case interview, you have to be nimble, creative, and spontaneous.
It's not like a vocabulary test that you can prepare for by memorizing a lot of words and roots. It's more like preparing for a chess match - you know the rules but don't know in advance which approach your opponent will take or in what situation you might find yourself.