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cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccclcccclccllccclclllllllllllllllllllllllllllllllllllllllllclllllllllllllllllllllllllllllllllllllllllllllllllc:l,'..;;c.;,cc;:';c:lllllllllllllllllllllllllllllllllllll cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccllcccccllccccccccllllllllllllllllllllllllllllllllllllllccllllllllllllllllllllllllllllllllllllllllllllllllllc:'.':,.c: .cccllc'';lllllllllllllllllllllllllllllllllllll cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccllccccccccccccclcllllllllllllllllllllllllllllllllllccllllllllllllllllllllllllllllllllllllllllllllllllllll;.:cl:lc.;.:.;lllll.'lllllllllllllllllllllllllllllllllllll 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cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccllccccccccccccclllllllllllllllllllllllllllllllllllcllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll;cc,'.';:o.:;,:,,',c;looooolooolooooollollllllllllllllllll ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccllccccccccccccccclllllllllllllllllllllllllllllllllcclllllllllllllllllllllllllllllllllllllllllllllllllllllllllllooo;l,':c;;c, .cl:llc,;;looooooooooooooollollllllllllllllllll cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccllclccllllllllllllllllllllllllllllllllllcllllllllllllllllllllllllllllllllllllllllllllllllllllllloooloooll.',;,',,.' .',;:::;' coooooooooooooooooooolloolooooolooool cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccllllllllllllllllllllllllllllllllllllclllllllllllllllllllllllllllllllllllllllllllllllllllllllolollllcc:. .,.,;lo;' ,',llllc' .:loooooooooooooooooooooooooooooooooo cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccclllclllllllllllllllllllllllllllllllllllcclllllllllllllllllllllllllllllllllllllllllllllllllllllllool:;,,,;::l''';';,,:. .c;.loo,.'colcclooooooooooooooooooooooooooooooo cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccllllllllllllllllllllllllllllllllllllllcclllllllllllllllllllllllllllllllllllllllllllllllll:,',::,,,',,.;:::loo'l'.c';l;, ',;'.:,;l;:oooolcccoooooooooooooooooooooooooooo cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccclllllllllllllllllllllllllllllllllllllllllcclllllllllllllllllllllllllllllllllllllllllllc;,',',;, . ...',,,;',;,,;'c;..',.cl :l:c..'::'.;ccccc::..:lllllllllllllllllllllllll cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccllccccccllllllllllllllllllllllllllllllllllllllllccllllllllllllllllllllllllllllllllllllllllll,.'',.'''. ......,,...'.....'..'....... ........'. .oooool;.,:c::ooooooooooooooooooolll cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccclllllccccllllllllllllllllllllllllllllllllllllllccllllllllllllllllllllllllllllllllllllllllllll;:lc:';;;'...,';;;,,;.',::;''.. ......c;, ,,cl:cc'',.'';cc,.;..,;;.,::cllllllllllllllllll cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccllllccccllllllllllllllllllllllllllllllllllllllllccllllllllllllllllllllllllllllllllllllllllllllll,.';..looool'cc:;,;;'.,:llll:c;.,.';.. . ;:;oooc,''lc,...,;cloocccoolcclooooooooooooooo ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccllcllllllllllllllllllllllllllllllllllllllllllllllcclllllllllllllllllllllllllllllllllllllllllllllll;..,..clooool,cllooooocc:;''''...;;'...... . .,...'.. ,cc'':';:lococ:oddool::loddooodooooo cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccclllllllllllllllllllllllllllllllllllllllllllllcclllllllllllllllllllllllllllllllllllllllllllllll:.....;looooool,coooooooooooooooc. ''''.;;.. . ''.,''. ,;,.',':c:',ll:ddolllo:lccloodddddoo cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccclcccccccclcclclcclllllllllllllllllllllllllllllllllllllllllllllclllllllllllllllllllllllllllllllllollllllllllllc:'.''..coooooooll;coooooooooooooooo,;.,;:c';;. '. ... . ,,..,'. .'....;cloooo:odlc:cloooooo ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccclcllcllllllcllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllolllollllll,'.....:,looooolooo:;oooooooooooooooo,ol. ',l:., ';cc. ..,'. ..'.',.cc:c.:;..';;,.::,,,;;',,;;; ccccccccccccccccccccccccccccccccccccccccccccccccccclccccccccccccccccccccccccccllllllllllllllllllllllllllllllllllllllllllllllllllllllllcllllllllllllllllllllllllllllllllllllloooooooooc:'. ..',cl,loolloooooc,oooooooooooooood'llc. ..,oo :d;..; .c:.;:'..;;;;::,;.::::',,::';:::::,lolcl ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccclcclllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllloooooooooo:c;..;,;ccol,clloooooool,oooooooooooddodd'ol'...';;: .',o;,:'.;,,odccdddolcc;';:;;c:c,,';cccc:'...', ccccccccccccccccccccccccccccccccccccccccccccccccccccccccclllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllloololoooooooooooooooolll::.,':ooool::oooooooooo;looooooooooodddo.:..:cc..o; :o;ldl'. :dd:cdddddddo:dddlccccc'......,;;,c: cccccccccccccccccccccccccccccccccccccccccccccccccccccccclllccclllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllooooooooloooooooooooooooooooooollllcl:;::loollol;oooooooooo;loooooodoooodddl 'lloldd;.. 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'c:;odo;. ...:;.,,..'coo:ld;ddddoccccddddddddd oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooodooddddddddddddddddddddoooooooodddddddddddddddddddddddddddddddddddddddddddooddddddddddddddddddddddo' .;.'dddxxxxxd::dddoc:,;,.',, .;lc,, .. .,,....',. ,:;'oc;,ll;oxx:xxxxdooccllldxxxxx oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooddoodddoddddddddddddddddddooooooooddddddddddddddddddddddddddddddddddddddddddoodddddddddddddddddddddddo,.....cddddxxxxxxl;dxxxxxxxxxxxd; ,,'.'.:;,'. ....,:',,,,. .,,:,,,...';lo:xdoodxxolxxxolloxx oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooodddodddddoddddddddddddddddddlooodooddddddddddddddddddddddddddddddddddddddddddoodddddddddddddddddddddddcc. '. ,ddddxxxxxxxxo;dxxxxxxxxxxxxx...xxccc,o:.. c; ...;co;. .;:,. ... .:dxxxxdcxxxxdl;,oProduction War Stories
I Shipped a Race Condition That Double-Charged Customers (And Other War Stories)
Nobody writes blog posts about the bugs they shipped. The internet is full of “how I built X” and suspiciously empty of “how I broke X and spent 14 hours pretending it wasn’t my fault.” Here are mine. The Race Condition: Two Cashiers, One Item This one happened in Polaris, the ERP system I built for retail businesses. Real money, real transactions, real angry shop owners. The setup: two cashiers at different terminals. Both scan the same product. Both hit “Complete Sale” within 200ms of each other. The inventory says there’s one left. ...