This happens frequently. 

You have to understand that client work is intense, and gets in the way of recruiting focus. To be honest, consulting firms are actually great with they reply times (i.e., in most corporates you have a less intense day-to-day and still they take much longer to give you an answer). So 7 days is more that acceptable.

Is it true that they could let a candidate wait until they could find another candidate to compare?

No, this is completely false. That applies to “unique roles”, i.e. roles that will only be filled out by one person, and they try to find the best candidate available (i.e. it is about beating the other candidates), and this is much more common in corporate. 

Here, you will be one of hundreds performing a similar role, so if they find multiple people passing the bar, they will extend them an offer. There's a bar, and if you pass the bar you get an offer, if you don't you're out.

Hi there,

It sounds very promising!

You just need to be patient here. The interview happened Tuesday - think about what has to happen in the background. The interviewers have to find a time to meet and discuss. They need to communicate decisions to HR. And HR has to track this in the system and reach out to you.

This is all happening across multiple candidates.

And, remember, you are not the priority of the interviewers (their clients, project teams, etc. are).

So, just be patient! It could be another week or two. If you have not heard back by the end of next week, then definitely reach out.

Fingers crossed for you!

I am in a similar situation as you with McKinsey, it is taking them longer to get back to me than it did for the first two interviews. I think this is normal, all the interviewers need to be debriefed again by HR not just the last interviewer. I guess this can explain the delay. You can always reach out to HR if you don't get any feedback by the end of next week.