How long did your US visa interview go on?

There should be options in secs, mine was less than a min

There are no tricky questions unless you try to be funny. Questions are about what you intend to with your visa and what your status is e.g. single or married, employed etc.

What type of visa? There are many different interviews, ranging from border security to marriage validity

Pretty easy interview until the immigration officer asked me to sort a linked list in O(1)

Tourist , L1 and even GC all took under 5 min. Cases were always perfect and had all the docs and requirements filled properly.