  The ALICE experiment at the LHC is undergoing a major upgrade during the Long
Shutdown 2 (2019-2021). In particular, the Time Projection Chamber (TPC) is
being equipped with new GEM-based readout chambers and the readout electronics
of several detectors are being replaced with faster and more flexible
technology. This will allow ALICE to read out most of the detectors in the
continuous mode and record minimum bias Pb-Pb events at rates of about 50 kHz
in Run 3 (2021-2024) and Run 4 (2027-2030). The ALICE Collaboration is also
considering the possibility to collect a large sample of proton-proton
collisions at interaction rates of about 1 MHz using online and offline
preselection of rare events. These goals require a completely new online
computing system that will be used to perform fast reconstruction and
compression of the data stream. The event selection strategy becomes especially
challenging for the case of central diffractive events and ultra-peripheral
Pb-Pb collisions characterized by rapidity gaps at forward and backward
directions with only few tracks at central rapidity. In this contribution, the
motivation for studying central diffractive and ultra-peripheral events is
presented, and feasibility studies for their selection in Run 3 and 4 will be
given.
