diff --git a/lib/degica_datadog/tracing.rb b/lib/degica_datadog/tracing.rb
index dced530..24e157e 100644
--- a/lib/degica_datadog/tracing.rb
+++ b/lib/degica_datadog/tracing.rb
@@ -49,6 +49,19 @@ def init(rake_tasks: []) # rubocop:disable Metrics/AbcSize,Metrics/MethodLength
           c.tracing.instrument :httpclient, split_by_domain: true
           c.tracing.instrument :httprb, split_by_domain: true
         end
+
+        # This block is called before traces are sent to the agent, and allows
+        # us to modify or filter them.
+        Datadog::Tracing.before_flush do |trace|
+          Datadog::Tracing::Pipeline::SpanProcessor.new do |span|
+            # Group subdomains in service tags together.
+            span.service = "myshopify.com" if span.service.end_with?("myshopify.com")
+            span.service = "ngrok.io" if span.service.end_with?("ngrok.io")
+            span.service = "ngrok-free.app" if span.service.end_with?("ngrok-free.app")
+          end
+
+          trace
+        end
       end
 
       # Start a new span.