perf(go): cache realtime plate lookups

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

@@ -114,6 +114,18 @@ func TestRealtimeAPIDoesNotExposeDuplicateMileagePointRoute(t *testing.T) {
 	}
 }
 
+func TestRealtimeAPICachesBindingPlateResolver(t *testing.T) {
+	source, err := os.ReadFile("main.go")
+	if err != nil {
+		t.Fatalf("read main.go: %v", err)
+	}
+	for _, want := range []string{"NewCachedPlateResolver", "PLATE_CACHE_TTL_SECONDS"} {
+		if !strings.Contains(string(source), want) {
+			t.Fatalf("realtime api should configure cached plate resolver, missing %s", want)
+		}
+	}
+}
+
 type contextCheckingRealtimeUpdater struct {
 	ctxErr error
 	count  int