A decade ago I brought the test time from 86min down to a few seconds. An intern had thought that synchronizing things with "sleep one tenth of a second then c

A decade ago I brought the test time from 86min down to a few seconds. An intern had thought that synchronizing things with "sleep one tenth of a second then check that flag again" at the heart of the product and reading and splitting by line a file where some lines might be 86Mo long were good ideas.