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Exactly what I thought. Microseconds? On HDD? That would mean the block is in RAM.

HDD latency is composed of seek + rotation latency + processing time, on the best of the best server HDDs random read might be in the ballpark of 10ms (10,000μs), desktop HDD... maybe around 30-40ms (30,000μs). Or ~600x times more than 49μs.

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Desktop HDDs aren't that bad, but 100 IOPS is a good ballpark for back of the envelope estimates (10ms). The OP wrote their B-Tree to require 3 lookups, so assuming they really are single disk reads that's where I calculated 30ms.

Just to confirm, the benchmarks are bad. Almost always the read parts of B-tree file are cached. I'll rewrite the benchmarks and update the results!

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