You wrote the query in an afternoon. It ran against your development database in four milliseconds, the test suite went green, and you shipped it. Six weeks later, someone in support forwards a screen...
Your app was fast for a year. Nothing changed — same code, same server, same query you wrote in an afternoon and never thought about again. Then one Tuesday the orders page takes eleven seconds to loa...
You wrote a function that worked perfectly on your laptop. It flew through a list of 50 names, sorted them, found the duplicates, and returned an answer in a blink. Then you shipped it, real users sho...
