* [**Breaking Change**] Optimize single trace query performance by customizing routing in ElasticSearch. SkyWalking trace segments and Zipkin spans are using trace ID for routing.
# Custom routing can reduce the impact of searches. Instead of having to fan out a search request to all the shards in an index, the request can be sent to just the shard that matches the specific routing value (or values).
# Custom routing can reduce the impact of searches. Instead of having to fan out a search request to all the shards in an index, the request can be sent to just the shard that matches the specific routing value (or values).