Anecdote: One of my managers once spent €70000¹ worth of hardware to speed up an application because he believed it would be cheaper than to optimize the code. Naturally, no-one had done any kind of performance analysis, so while the upgrade made things about 20% faster, it still wasn't enough. It took me all of 20 minutes to figure out that caching was disabled on the database and it had no indexes whatsoever². 30 minutes of work yielded a few thousand percent speed increase.
¹) This was a long time ago before SSDs existed and buying a hardware RAID of fast disks and fast CPUs / memory was extremely expensive.
²) DBAer consultants of a certain large database vendor are not worth the horrendous hourly fee they ask.
