plan.sortedNodes().stream()
                        // 1. Filter steps that are in CREATED state
                        .filter(BuildStep::isCreated)
                        // 2. Check if all predecessors are in a terminal state
                        .filter(step -> step.predecessors.stream().allMatch(BuildStep::isDone))
                        // 3. Process each step

		d.Policy = doc.Policy
		return nil
	}
	*d = doc
	return nil
}

// key options
type options struct {
	ttl int64 // expiry in seconds
}

type iamWatchEvent struct {
	isCreated bool // !isCreated implies a delete event.
	keyPath   string
}

// iamCache contains in-memory cache of IAM data.
type iamCache struct {
	updatedAt time.Time

	// map of policy names to policy definitions