Where things get interesting is the mismatch between Big-O data structure complexity analysis (as typically discussed in interviews) and actually knowing about the hardware, the operating system, the memory hierarchy and things like cost of context switches and cache misses.
Some real-life practical examples: knowing when a simple O(n) linear search beats O(log n) binary search, or knowing when a multiple substring search algorithm based on a simple Rabin-Karp and L1 cached hash table lookup will outperform the theoretically more optimal Aho-Corasick.
Some real-life practical examples: knowing when a simple O(n) linear search beats O(log n) binary search, or knowing when a multiple substring search algorithm based on a simple Rabin-Karp and L1 cached hash table lookup will outperform the theoretically more optimal Aho-Corasick.