This could be done on a document or a spreadsheet.  The advantage of a spreadsheet is that you could lock some of the columns or rows so that students could not change the data.  

The teacher posts a prompt in a document or sheet. Have each student write an entry and then read their partners and comment or question on what they read.  Teachers would monitor the time and give students verbal feedback about the amount of time left.

You could also do this with Private Chats or Breakout Rooms but be mindful that you may not always be able to monitor these chats.