The wall time limit was imposed to mitigate the effects of problematic regions of chemical space where the number of possible next actions per molecule, and therefore the time required to enumerate them, vastly outnumbered typical molecules. This was typically encountered with molecules with many possible tautomers and resulted in rollouts being added to the replay buffer that used an outdated version of the policy model. Communication between the policy network training script and the MCTS rollout workers is handled through a shared filesystem and a PostgreSQL server. Policy checkpoints are previously written to a shared filesystem location, which is checked at the beginning of each rollout by the workers.