System design interview question
"Design a real-time collaborative document editor. Several people type in the same document simultaneously, each sees the others' changes within a fraction of a second, everyone's copy converges to the same result, and it works offline with changes merging on reconnect."
concurrent editing convergence, which is one of the few genuinely deep algorithmic problems in system design. The core difficulty is that two users editing the same text at the same moment produce operations whose meaning depends on each other, and naive application produces divergent documents. The candidate must reach either operational transformation or CRDTs and explain why simpler approaches fail.
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