End-to-End Design
Design a collaborative document editor: many people open the same document and type into it at once, every keystroke shows up for the others within a moment, and everyone's screen converges to the identical text with no edit ever silently lost.
In scope: concurrent text editing, real-time propagation of edits, presence (cursors and selections), and reconnecting after being offline. Rich formatting beyond plain text, sharing permissions, and peer-to-peer editing without a server are variants, covered briefly at the end.
What a strong answer sounds like
State the decision, connect it to a requirement, and name the tradeoff. Keep the design focused on the workload in the prompt.
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