A few days ago, I was called for an interview in Soliton Tech for job. At the moment I'm kinda jobless so I needed this one.
They were in search for a mongodb expert. I'm not mongodb expert but I know Cassandra. Cassandra is also a database. NoSQL in nature, just like mongo-db. So, they first had an interview with me on the phone and they were satisfied that I was the person they were looking for. But then I was called for an interview face to face. They also told me that I should prepare myself for mongodb, just-in-case if anything related to mongodb is asked in the interview.
So I spent two days on mongodb. Though it wasn't very tough for me because I already have an idea how these databases look like. I still spent my time with it to know as much as I could about that database.
On the day of interview, I went, I was there on time. And three people came to interview me. I was satisfied that I know enough, I can answer anything they ask.
But still, I was going for an interview and the people who were going to interview were all very knowledgeable (in my opinion) so there was a bit of fear too. This is where everything went wrong.
So, they asked me question related to cassandra. But hey, I never saw anything like that in Cassandra! and anyway I answered them to the best of my knowledge, and they started to negate on everything I said. So much that I got confused that everything I ever learned was perhaps a lie.
They were asking me question that I never expected, for example, how do you create primary keys in cassandra? or compound keys?
For example he asked me "If I'm making a database for school, then how the student keys will be created, what should be the primary key?"
Now this is a question which can have lots and lots of answers. Usually the student's roll no. is a primary key. So that's what I said. But the problem is, cassandra doesn't have a fucking auto-increment like mysql does. So they suggested some ridiculous solutions and I accepted them. But in a real world, those solutions doesn't work. We must create a simple primary key so for that some third party softwares are used. Cassandra can't do that.
Now all the questions they asked were almost just like that. I answered them according to what I thought the interviewers wanted to listen. But then, that was not what they wanted to listen.
For example, he said how is data stored on a hard-disk. I said sequentially, but he refused, he said that sql server stores data in form of a tree. I said ok I haven't worked in ms-sql server so I can't say anything.
Anyway, they weren't satisfied with my answers I could easily guess that.
So, I came home, confused, and then I started to do a research about everything I said and everything they said, and I came to know... that I was right!
They either didn't know, or were trying to confuse me.
Anyway, I learned the lesson, whenever go for an interview, take the interviewer as an idiot!