busoni, you need to shut down Poloniex now and try to make your users whole from your own funds and debt. Do not continue trying to run an exchange. Your post mortem indicates that you do not have sufficient programming ability to handle other peoples money - no mention was even made of database transactions, which are a basic "database programming 101" topic. Your proposed fix of checking for negative balances is wrong and indicates that your code is almost certainly riddled with other exploitable bugs.
Please do the right thing and refund everyones outstanding balances, then wind up your operation.
This comment was from Mike Hearn, senior developer at google.
And yes mike is right. The developer of Poloniex have no knowledge about database transactions and handle code in multithreaded environment.
holy fuck get out of town! some lackey for the great satan of our age says shit is fucked? I have to go change my diaper cause I am shitting my pants. Hows about the cunts at google stick to war profiteering from the internets and our privacy and leave the cryptos to us delusional asses.
Next lets get some zombie Rocefeller's to give financial advice. What the fuck are you dumb shits thinking?