Fast Hints Checkpoint

Estimation, measurement, memory layout, and avoiding unnecessary work.

Get every question correct to pass this checkpoint. You can review feedback, revise your answers, and submit again.

1. A 100 ms request spends 10 ms formatting. Formatting becomes twice as fast; other costs stay fixed. New total?

Select one answer.

50 ms 95 ms 90 ms 80 ms

2. A batch API reduces per-item overhead but raises p99 waiting time. What should determine whether to keep it?

Select one answer.

The throughput and latency requirements measured on representative load The assumption that batching is always faster Only the highest throughput number Only the smallest batch size

3. A microbenchmark improves while production slows. What evidence is most useful next?

Select one answer.

More runs of only the same tiny input Assuming the production measurements are invalid A representative profile including allocation, contention, and input distribution Removing correctness checks from the product

4. A task takes 80 ms, of which 20 ms is a completely removable cost. What is the best total time if other work is unchanged? Answer with the integer number of milliseconds only.

5. Four workers spend most time waiting for one lock. Which experiment tests the suspected bottleneck?

Select one answer.

Compare lock wait and throughput after partitioning independent state Add workers without measuring Increase object size Remove ordering requirements without checking correctness

6. A pool retains very large buffers after rare requests. Which comparison is needed before claiming an improvement?

Select one answer.

Only pool hit count Only binary size Only the fastest request Both allocation rate and retained memory under mixed request sizes

7. EncodeKeys sorts the dictionary and adjusts every ID. Reconstruction still succeeds. Is that sufficient for correctness?

Select one answer.

No; the dictionary must preserve first-occurrence order Yes; any order is accepted Yes; sorting always reduces retained memory No; integer IDs cannot reconstruct strings

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