  Flavour changing neutral current (FCNC) processes are described by loop
diagrams in the Standard Model (SM), while in 331 models, based on the gauge
group $\text{SU}(3)_C \times \text{SU}(3)_L \times \text{U}(1)_X$, they are
dominated by tree-level exchanges of a new heavy neutral gauge boson $Z'$.
Exploiting this feature, observables related to FCNC decays of $K$, $B_d$ and
$B_s$ mesons can be considered in several variants of 331 models. The variants
are distinguished by the value of a parameter $\beta$ that plays a key role in
this framework. Imposing constraints on the $\Delta F = 2$ observables, we
select possible ranges for the mass of the $Z'$ boson in correspondence to the
values $\beta = \pm k / \sqrt{3}$, with $k = 1, 2$. The results are used to
determine the impact of 331 models on $b \to s$ processes and on the
correlations among them, in the light of new experimental data recently
released.
