  In this short expository note, we prove the following result, which is a
special case of the main theorem in arXiv:2011.09451. For each $n \ge 2$ and
$p, q \in [2, \infty]$, we prove upper bounds of $\ell^q(L^p)$ decoupling
constants for paraboloids in $\mathbb R^n$, as well as presenting extremisers
for each case. Both are sharp up to $\varepsilon$-losses.
