perf(go): cache identity binding lookups

go/vehicle-gateway/cmd/gateway/main_test.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"os"
+	"strings"
 	"testing"
 
 	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
@@ -32,6 +34,18 @@ func TestNATSSinkConfigFromEnvUsesExplicitSubjects(t *testing.T) {
 	}
 }
 
+func TestGatewayConfiguresIdentityLookupCacheTTL(t *testing.T) {
+	source, err := os.ReadFile("main.go")
+	if err != nil {
+		t.Fatalf("read main.go: %v", err)
+	}
+	for _, want := range []string{"LookupCacheTTL", "IDENTITY_LOOKUP_CACHE_TTL_SECONDS"} {
+		if !strings.Contains(string(source), want) {
+			t.Fatalf("gateway should expose identity lookup cache ttl, missing %s", want)
+		}
+	}
+}
+
 func TestNATSSinkConfigFromEnvDefaultsToGoSubjects(t *testing.T) {
 	t.Setenv("NATS_URL", "nats://172.17.111.56:4222")