  We study the stability of quasinormal modes (QNMs) in electrically charged
black brane spacetimes that asymptote to AdS by means of the pseudospectrum.
Methodologically, we adopt ingoing Eddington-Finkelstein coordinates to cast
QNMs in terms of a generalised eigenvalue problem involving a non-selfadjoint
operator; this simplifies the computation significantly in comparison with
previous results in the literature. Our analysis reveals spectral instability
for (neutral) scalar as well as gravitoelectric perturbations. This indicates
that the equilibration process of perturbed black branes is sensitive to
external perturbations. Particular attention is given on the hydrodynamic
modes, which are found to be the least unstable. In contrast with computations
in hyperboloidal coordinates, we find that the pseudospectral contour lines
cross to the upper half plane. This indicates the existence of
pseudo-resonances as well as the possibility of transient instabilities. We
also investigate the asymptotic structure of pseudospectral contour levels and
we find remarkable universality across all sectors, persistent in the extremal
limit.
