Replication choices: Can database replication be implemented with either synchronous or asynchronous techniques, with asynchronous being more common in practice?
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AApplies — both modes exist and async is commonly deployed
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BDoes not apply — only synchronous replication is supported
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CApplies only to key–value stores
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DApplies only on shared-disk architectures
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EApplies only when using two-phase commit
Answer
Correct Answer: Applies — both modes exist and async is commonly deployed
Explanation
Introduction / Context:Choosing replication mode is a key architectural decision that balances latency, consistency, and durability.
Given Data / Assumptions:
- Synchronous replication adds commit latency but strong consistency.
- Asynchronous replication lowers latency but allows temporary divergence.
- Many production systems prioritize throughput and availability, making async prevalent.
Concept / Approach:Both modes are widely supported. Asynchronous replication is often favored for geo-distribution and large-scale read-heavy services because it reduces user-visible latency and tolerates WAN variability.
Step-by-Step Solution:Define synchronous vs. asynchronous semantics.Map them to operational trade-offs (latency vs. consistency).Recognize industry practice: async is common for DR and global read replicas.Conclude the statement is valid.
Verification / Alternative check:Vendor documentation typically offers both modes with tuning for durability and lag monitoring.
Why Other Options Are Wrong:Limiting to a single mode or architecture is incorrect; 2PC is related to distributed commit, not required for all replication styles.
Common Pitfalls:Assuming async guarantees no data loss in catastrophic failures; SLA design must specify RPO/RTO.
Final Answer:Applies — both modes exist and async is commonly deployed