  We revisit the possibility of a Dirac fermion dark matter candidate in the
light of current $b \to s \ell^+ \ell^-$ anomalies by investigating a minimal
extension of the Standard Model with a horizontal $\mathrm{U(1)}^{\prime}$
local symmetry. Dark matter stability is protected by a remnant $\mathcal{Z}_2$
symmetry arising after spontaneous symmetry breaking of
$\mathrm{U(1)}^{\prime}$. The associated $Z^{\prime}$ gauge boson can
accommodate current hints of new physics in $b \to s \ell^+ \ell^-$ decays, and
acts as a vector portal between dark matter and the visible sector. We find
that the model is severely constrained by a combination of precision
measurements at flavour factories, LHC searches for dilepton resonances, as
well as direct and indirect dark matter searches. Despite this, viable regions
of the parameter space accommodating the observed dark matter relic abundance
and the $b \to s \ell^+ \ell^-$ anomalies still persist for dark matter and
$Z^{\prime}$ masses in the TeV range.
