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You wrote a formula to calculate WCUs as: WCUs = item size in KB / 4. Why might this be incorrect?

medium📝 Debug Q6 of 15
DynamoDB - Cost Optimization and Monitoring
You wrote a formula to calculate WCUs as: WCUs = item size in KB / 4. Why might this be incorrect?
ABecause item size should be divided by 2 KB
BBecause WCUs depend on read consistency
CBecause write capacity units are based on 1 KB increments, not 4 KB
DBecause WCUs are fixed per table
Step-by-Step Solution
Solution:

  1. Step 1: Recall WCU calculation basis

    Write capacity units are charged per 1 KB of data written, so dividing by 4 KB is incorrect.

  2. Step 2: Identify correct divisor

    The divisor should be 1 KB to correctly calculate WCUs.

  3. Final Answer:

    Because write capacity units are based on 1 KB increments, not 4 KB -> Option C

  4. Quick Check:

    WCU divisor = 1 KB, not 4 KB [OK]
Quick Trick: Writes count per 1 KB, not 4 KB [OK]
Common Mistakes:
MISTAKES
  • Using 4 KB divisor for writes
  • Confusing read and write unit sizes
  • Assuming WCUs are fixed

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