All the code which is not in hot path may conform to any rules, and typically is designed according to something like SOLID, to make understanding and maintenance as simple as possible (and suitable to any average coder).
All the code which performance, memory cost, etc. is critical, should be adjusted to fit into required confine even if it will violate all other tenets. This often results in combination of opposite approaches - anything that does well.
Finally, one just profiles the code and fixes all most spending paths. This is what now any average programmer can do. What it canʼt do - and what Carmack has been doing for decades - is to predict such places and fixes them proactively at architectural level; and to find tricky solutions that average joe-the-programmer hasnʼt heard ever.
All the code which performance, memory cost, etc. is critical, should be adjusted to fit into required confine even if it will violate all other tenets. This often results in combination of opposite approaches - anything that does well.
Finally, one just profiles the code and fixes all most spending paths. This is what now any average programmer can do. What it canʼt do - and what Carmack has been doing for decades - is to predict such places and fixes them proactively at architectural level; and to find tricky solutions that average joe-the-programmer hasnʼt heard ever.