The two-digit lookup table that makes integer-to-string conversion 31% faster
Integer to String Conversion (2014)
L. Pereira recounts optimizing integer-to-string conversion in Lwan, from snprintf to a naive reverse-and-divide method, then to a backward-writing approach. He admits committing an unmeasured change (lookup table to addition) that was actually 9% slower. Facebook's two-digit lookup table halves divisions and runs 31% faster, but licensing prevents its use in Lwan.
However, I eventually did what one should always avoid when tinkering with this kind of thing: I've changed the array lookup to an addition, without measuring if it would perform better, and committed the code anyway. The lookup table is ~9% faster. Ouch!