We use an undo stack on the browser side. We realized that it was better not to share this change log between users. Also we do not persist it. But your mileage

We use an undo stack on the browser side. We realized that it was better not to share this change log between users. Also we do not persist it. But your mileage may vary depending on your needs. In an older app the undo stack was zipped and serialized in db. With zip you avoid storing too much with every character added to 5 pages of text and you do not have to work with diff's.