I already saw such a colleague training hard at competitive programming, everyday. Yet, he wrote that kind of C++ code:

  ressource AClass::CopyACriticalRessource()
  {     
     {
        std::lock l;
     } // Optimization for the lock.
     
     return ressource_;
  }

Having a good understanding of every aspect of your architecture, taking your time instead of rushing for blazing fast (O(1)) but hacky solution, always having in mind that someone must have already solved your problem... these are some valuable skills not coverable during a 1h interview in front of a white board. I would like someone googling a solution in front of me during an interview, trying to UNDERSTAND it, check its complexity, compare it with other search hits, adapt it to his problem, ask for my review.

The best technical interview being a homework with enough time for a normal human being, requiring tricky algorithms to solve it in a fancy way, a good architecture and great computer-science knowledge in general. Afterwards, a code-review/interview of 1 hour with debriefing on all the choices.