at first I was looking for a bigass long backpack I can go travelling/hiking with but after I realized I won't be doing much of that so I better get something that can fit in a locker or under a seat.

It needs to be sturdy enough. I plan on carrying about 20lbs of groceries every once in a while (mostly when I buy 8kg/16,7lbs bag of rice.)

a laptop compartment would be a nice extra