What is the index-shift problem in concurrent editing?
When two users concurrently edit a string at different positions, the operations carry indices valid only against the state each user saw. If you naively apply the second operation at its original index against the first user's modified state, the result is wrong—you delete or insert at the wrong position because the indices have shifted.
Answered in
Operational Transforms vs CRDTsWhy Google Docs needs a server and Figma doesn't: how two competing approaches to concurrent editing resolve the same-string conflict, and when each wins.
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