  The Belle II experiment at the SuperKEKB electron-positron collider aims to
collect an unprecedented data set of $50~{\rm ab}^{-1}$ to study $CP$-violation
in the $B$-meson system and to search for Physics beyond the Standard Model.
SuperKEKB is already the world's highest-luminosity collider. In order to
collect the planned data set within approximately one decade, the target is to
reach a peak luminosity of $\rm 6 \times 10^{35}~cm^{-2}s^{-1}$ by further
increasing the beam currents and reducing the beam size at the interaction
point by squeezing the betatron function down to $\beta^{*}_{\rm y}=\rm
0.3~mm$. To ensure detector longevity and maintain good reconstruction
performance, beam backgrounds must remain well controlled. We report on current
background rates in Belle II and compare these against simulation. We find that
a number of recent refinements have significantly improved the background
simulation accuracy. Finally, we estimate the safety margins going forward. We
predict that backgrounds should remain high but acceptable until a luminosity
of at least $\rm 2.8 \times 10^{35}~cm^{-2}s^{-1}$ is reached for
$\beta^{*}_{\rm y}=\rm 0.6~mm$. At this point, the most vulnerable Belle II
detectors, the Time-of-Propagation (TOP) particle identification system and the
Central Drift Chamber (CDC), have predicted background hit rates from
single-beam and luminosity backgrounds that add up to approximately half of the
maximum acceptable rates.
