val reuseCallConnection = planReuseCallConnection()
    if (reuseCallConnection != null) return reuseCallConnection

    // Attempt to get a connection from the pool.
    val pooled1 = planReusePooledConnection()
    if (pooled1 != null) return pooled1

    // Attempt a deferred plan before new routes.
    if (deferredPlans.isNotEmpty()) return deferredPlans.removeFirst()