  Missing transverse momentum is a crucial observable for physics at hadron
colliders, being the only constraint on the kinematics of "invisible" objects
such as neutrinos and hypothetical dark matter particles. Computing missing
transverse momentum at the highest possible precision, particularly in
experiments at the energy frontier, can be a challenging procedure due to
ambiguities in the distribution of energy and momentum between many
reconstructed particle candidates. This paper describes a novel solution for
efficiently encoding information required for the computation of missing
transverse momentum given arbitrary selection criteria for the constituent
reconstructed objects. Pileup suppression using information from both the
calorimeter and the inner detector is an integral component of the
reconstruction procedure. Energy calibration and systematic variations are
naturally supported. Following this strategy, the ATLAS Collaboration has been
able to optimise the use of missing transverse momentum in diverse analyses
throughout Runs 2 and 3 of the Large Hadron Collider and for future analyses.
