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Flip to reveal answersReplication or fragmentation — what is the difference?
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All 5 Flashcards — Distributed databases
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Question
Replication or fragmentation — what is the difference?
Answer
**Replication** keeps copies of the same data (availability, read speed). **Fragmentation** splits data between machines (capacity, writes).
Question
What happens if a shard's machine fails?
Answer
**That portion becomes unavailable** — unless the shard is also replicated, which is why real systems do both.
Question
What is the consistency–availability trade-off?
Answer
During a network partition you either **refuse to answer** (consistent) or **answer from a reachable copy** (available, possibly stale). You cannot have both.
Question
Which would a bank choose, and which a social feed?
Answer
A bank chooses **consistency** — better to refuse than to allow a double withdrawal. A social feed chooses **availability** — a late post is harmless.
Question
What is eventual consistency?
Answer
Copies are brought into step **shortly after** a write, not instantly — so a read straight after a write can return the old value.
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