  We perform a complete study of the low-energy phenomenology of $S_1$ and
$S_3$ lepto-quarks, aimed at addressing the observed deviations in $B$-meson
decays and the muon magnetic dipole moment. Leptoquark contributions to
observables are computed at one-loop accuracy in an effective field theory
approach, using the recently published complete one-loop matching of these
leptoquarks to the Standard Model effective field theory. We present several
scenarios, discussing in each case the preferred parameter space and the most
relevant observables.
