I'd say that for widely used library code it makes sense to implement an efficient algorithm. By its very nature the context in which a library routine will be called is unknown and so it must be prepared for everything. Also for widely used code the amount of total saved machine time can be quite substantial.

In the story the senior dev makes a judgment call (that this routine will be used in LOB applications where the worst case is unlikely to appear so the implementation is OK) which is probably correct, especially considering other priorities. And of course senior devs are much better equipped to make this kind of calls than juniors, but they still can and will guess wrong.

> Moreover, Tim explained to me, any solution that involves allocating a table, preprocessing strings, and so on, is going to take longer to do all that stuff than the blazingly-fast-99.9999%-of-the-time brute force algorithm takes to just give you the answer.

That's why a good implementation will dispatch to the best algorithm at runtime!