  The XENON1T liquid xenon time projection chamber is the most sensitive
detector built to date for the measurement of direct interactions of weakly
interacting massive particles with normal matter. The data acquisition system
(DAQ) is constructed from commercial, open source, and custom components to
digitize signals from the detector and store them for later analysis. The
system achieves an extremely low signal threshold below a tenth of a
photoelectron using a parallelized readout with the global trigger deferred to
a later, software stage. The event identification is based on MongoDB database
queries and has over 97% efficiency at recognizing interactions at the analysis
energy threshold. A readout bandwidth over 300 MB/s is reached in calibration
modes and is further expandable via parallelization. This DAQ system was
successfully used during three years of operation of XENON1T.
