Why does increasing Kaspa's block rate make validation harder?

Raising Kaspa's block rate increases the cost of the difficulty adjustment algorithm at a squared rate. The algorithm works by maintaining, for each block, a list of past blocks with the highest accumulated weight — and that list must be traversed every time a block is validated. If the block rate increases by a factor of R, validation complexity grows by R²: one factor because each block requires R times more steps to validate, and a second factor because blocks arrive R times faster. This matters for anyone following Kaspa's technical roadmap: any upgrade that raises the block rate must also find ways to keep this overhead manageable, which is exactly what the current improvement proposal addresses.