Cap Theorem easy
Which of these is a typical use case for an AP (Available + Partition Tolerant) design?
- A A Retail Bank ATM performing a real-time cash withdrawal from a high-value account.
- B A High-Frequency Stock Trading engine executing thousands of trades per millisecond.
- C A centralized nuclear launch control system that requires unanimous consensus from all nodes.
- D A Social Media News Feed where it is acceptable if a post appears a few seconds late for some users.
Answer: D. A Social Media News Feed where it is acceptable if a post appears a few seconds late for some users.
For a social media feed, user engagement (Availability) is usually more important than absolute real-time correctness (Consistency). It is better to show 'stale' data than to show an error message and block the user entirely. This choice optimizes for user experience in high-traffic, non-critical scenarios. In contrast, financial or safety-critical systems must prioritize Consistency (CP) to avoid dangerous errors like double-spending.
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