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System Design Expert — Series 2
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A replicated-log system promises that acknowledged writes survive any one-node failure. What acknowledgment boundary supports that promise in a three-voter crash-fault model?
AAcknowledge immediately after issuing an asynchronous replication send.
BAcknowledge after writing only the leader's volatile memory.
CAcknowledge when one follower receives bytes but before required durability.
DDurably commit through the protocol's majority before acknowledging.
A multi-region register uses last-write-wins merge. Two concurrent values conflict. What can be claimed safely?
AIt preserves every distinct value in the final single-value register.
BIt reconstructs the exact real-time order despite unsynchronized clocks.
CIt provides serializable transactions across arbitrary records.
DIt can converge deterministically while discarding a concurrent value.
A player estimates bandwidth from a brief fast burst and requests a high-bitrate next segment. What protects against repeated rebuffering when bandwidth varies?
ASwitch quality only once at the beginning of the full video.
BDownload every bitrate variant for each segment before playing it.
CAlways pick the highest variant observed during any past segment.
DUse buffered duration and conservative bandwidth estimates when selecting quality.
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