I am a bit concerned that the ShardRegion actor may be a bottleneck in an application I am building. From what I understand, all messages to a specific shard region passes through the ShardRegion actor before forwarding the message to the appropriate shard and finally delivered to the entity (ShardRegion -> Shard -> Entity). Are messages to the ShardRegion serialized (consumed sequentially)? Or is the ShardRegion actor a “special” actor like a router? If the former is true, it seems like this would be a huge limit to scalability if there are hundreds or thousands of entities under a ShardRegion actor. How should shards be built to avoid the sequential bottleneck in that case?