Policy Simulator is a collection of endpoints for creating, running, and viewing a [Replay][google.cloud.policysimulator.v1.Replay]. A `Replay` is a type of simulation that lets you see how your members' access to resources might change if you changed your IAM policy. During a `Replay`, Policy Simulator re-evaluates, or replays, past access attempts under both the current policy and your proposed policy, and compares those results to determine how your members' access might change under the proposed policy.