There could be infinitely many reasons for this kind of slow software, but most cases many programmers don't care what happens under the hood as long as their c

There could be infinitely many reasons for this kind of slow software, but most cases many programmers don't care what happens under the hood as long as their code over abstraction layers appears to be working as intended in their own test scenario. I saw many websites developed by someone who doesn't really understand how query plans are generated and executed, how data is indexed, etc... and in the result they accidentally write the query that simply scans over the entire table. And thanks to modern hardware and database engine this scales to hundreds or even thousands of users!