H1B, H4 Visa

I completed six years stay at US on H1B Visa and I got 3 years extension last month as my I-140 got approved.
I came to India on vacation few days back and went to Chennai for Visa interview.

Me: Good Morning Madam
Visa Officer: Good Morning
Visa Officer: Which company you are going to work for?
Me: I am working for XYZ
Visa Officer: Are you on vacation
Me: Yes madam
Visa Officer: How long you are working with them
Me: Since Nov 2008, it is almost 3 years

Visa Officer: Are you working at client place?
Me: Yes madam. xyz is the client
Visa Officer: Is there a vendor in between?
ME: yes madam. "abc" is vendor.
Visa Officer: how long your H1 petition is valid
Me: 3 more years, till sept 2014
Visa Officer: How long you are planning to work at US
Me: As long as my petition is valid
Visa Officer: What is your highest qualification
Me: Masters in Software systems
Visa Officer: Who is you manager
Me: ABC is my client manager
Visa Officer: Who is your overall manager
Me: XYZ
Visa Officer: Which company he works for, your vendor company?
Me: No madam. He works for my company
Visa Officer: How often you talk to him
Me: Once in week.
Visa Officer: Explain about your project
Me: Explained briefly in 3-4 sentences.
Visa Officer: Who use those products
Me: Client’s customers
Visa Officer: Your Visa is approved. You will get passport by courier
Me: Thank you madam.

She did not ask any documentation other than DS-160 form confirmation page, I-797 original and my passport
Visa officer is asking questions and cross checking our answers with information provided in I-129 petition. They can access your I-129 application based on your petition no. So read your I-129 petition filed by your employer thoroughly before going for interview.