  Starting in 2022, the upgraded LHCb detector will collect data with a pure
software trigger. In its first stage, reducing the rate from 30MHz to about
1MHz, GPUs are used to reconstruct and trigger on B and D meson topologies and
high-pT objects in the event. In its second stage, a CPU farm is used to
reconstruct the full event and perform candidate selections, which are
persisted for offline use with an output rate of about 10 GB/s. Fast data
processing, flexible and custom-designed data structures tailored for SIMD
architectures and efficient storage of the intermediate data at various steps
of the processing pipeline onto persistent media, e.g. tapes is essential to
guarantee the full physics program of LHCb. In this talk, we will present the
event model and data persistency developments for the trigger of LHCb in Run 3.
Particular emphasize will be given to the novel software-design aspects with
respect to the Run 1+2 data taking, the performance improvements which can be
achieved and the experience of restructuring a major part of the reconstruction
software in a large HEP experiment.
