[growse]

The right lesson to learn here is "manage and maintain your software as it's used in the real world, as that will tell you where you need to invest time" not "prematurely optimize every algorithm just in case it becomes a problem".

[stouset]

No, the right lesson here is that quadratic algorithms are a particularly nasty middle ground of seeming to work for the small n of development and initial rollout but falling over for the medium to large n of living in production.

Luckily they’re typically easy to notice, and better approaches are often as easy as sorting your input first or caching items in a hash table.

An engineer should therefore catch these things when writing them or in code review and make sure a slightly better option is used in any situation where the size of input has a reasonable chance of growing.

The cost is nearly nothing and the benefit is not shipping code that will virtually guarantee slow response times and bloated scaling costs at best and humans being woken up at night for outages at worst.