What is a behavioral interview?

You have passed the coding round. The next interviewer opens with "Tell me about a time you disagreed with a teammate." There is no whiteboard and no problem to solve. This is the behavioral interview, and most engineers arrive at it with no preparation at all.

What it is

A behavioral interview is a round where the interviewer asks about things you have already done, rather than problems you might solve. The questions almost always start the same way. "Tell me about a time when..." or "Describe a situation where..."

The idea behind it is simple. How you behaved in a real situation is better evidence than what you say you would do in an imagined one. Anyone can describe how they would handle a difficult teammate. Fewer people can describe how they actually did.

What the interviewer is doing

They are not having a conversation. They are collecting evidence.

Most large companies give the interviewer a list of things to look for. Common items are how you handle conflict, how you decide with incomplete information, and whether you take responsibility for results. The interviewer writes down what you say and marks it against that list. Afterwards they write a summary that other people read.

This changes how you should answer. A story that is pleasant to listen to but contains no evidence scores nothing. The interviewer needs specific things to write down: what the situation was, what you personally did, and what changed as a result.

Questions you should expect

Here are five, in some form:

1. Tell me about a time when you had to deal with a difficult team member.
2. Describe a situation where you had to solve a complex problem.
3. Give an example of a time when you had to meet a tight deadline.
4. Tell me about a time you failed.
5. Tell me about a time you disagreed with your manager.

These are broad on purpose. The interviewer wants to see which experience you choose first, because that choice tells them something on its own.

How it differs from the technical round

In a technical round the problem is given to you. In a behavioral round you supply both the problem and the answer, and you are judged on both.

That is why preparation works so well here. You cannot know which coding question is coming. You can prepare six or seven stories in advance and cover most of what this round will ask.

What it is not

It is not a personality test, and there is no correct personality. Interviewers are not deciding whether they like you. They are deciding whether the evidence you gave matches what the role needs.

It is also not a formality. At most large companies this round is scored the same way the technical rounds are. A weak result here can end the process on its own.