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PCDE Practice Question: Design innovative, scalable, and highly available cloud database solutions

You need to estimate the number of Bigtable nodes required for a workload of 50,000 reads per second (QPS) and 20,000 writes per second. Each node can handle 10,000 QPS for reads or writes. Storage is not a constraint. What is the minimum number of nodes required?

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

5 nodes

Reads require 50,000/10,000 = 5 nodes. Writes require 20,000/10,000 = 2 nodes. The higher value is the bottleneck, so 5 nodes are needed.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • 2 nodes

    Why it's wrong here

    Insufficient for read throughput.

  • 7 nodes

    Why it's wrong here

    Over-provisioned; 5 nodes are sufficient.

  • 5 nodes

    Why this is correct

    5 nodes provide 50,000 QPS read and 50,000 QPS write, meeting both requirements.

  • 10 nodes

    Why it's wrong here

    Unnecessarily high.

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Written by Johnson Ajibi, MSc IT Security

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