  In this paper, we consider the $K$-user cache-aided wireless MISO broadcast
channel (BC) with random fading and delayed CSIT, and identify the optimal
cache-aided degrees-of-freedom (DoF) performance within a factor of 4. The
achieved performance is due to a scheme that combines basic coded-caching with
MAT-type schemes, and which efficiently exploits the prospective-hindsight
similarities between these two methods. This delivers a powerful synergy
between coded caching and delayed feedback, in the sense that the total
synergistic DoF-gain can be much larger than the sum of the individual gains
from delayed CSIT and from coded caching.
  The derived performance interestingly reveals --- for the first time ---
substantial DoF gains from coded caching, even when the (normalized) cache size
$\gamma$ (fraction of the library stored at each receiving device) is very
small. Specifically, a microscopic $\gamma \approx e^{-G}$ can come within a
factor of $G$ from the interference-free optimal. For example, storing at each
device only a \emph{thousandth} of what is deemed as `popular' content
($\gamma\approx 10^{-3}$), we approach the interference-free optimal within a
factor of $ln(10^3) \approx 7$ (per user DoF of $1/7$), for any number of
users. This result carries an additional practical ramification as it reveals
how to use coded caching to essentially buffer CSI, thus partially ameliorating
the burden of having to acquire real-time CSIT.
