diff --git a/resolver-go/cmd/api-server/main.go b/resolver-go/cmd/api-server/main.go
index 8d53463..bf03610 100644
--- a/resolver-go/cmd/api-server/main.go
+++ b/resolver-go/cmd/api-server/main.go
@@ -5,6 +5,7 @@ import (
 	"log"
 	"net/http"
 	"strings"
+	"time"
 
 	"github.com/tgckpg/resolver-go/internal/closure"
 	"github.com/tgckpg/resolver-go/internal/generated"
@@ -62,6 +63,7 @@ func (h handler) index(w http.ResponseWriter, req *http.Request) {
 		return
 	}
 
+	timerStart := time.Now()
 	res, err := h.r.ResolveRequest(code, outMode, nil)
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusNotFound)
@@ -72,6 +74,8 @@ func (h handler) index(w http.ResponseWriter, req *http.Request) {
 		if compiled, ok := h.closure.Get(res.Hash); ok {
 			w.Header().Set("Content-Type", "application/javascript")
 			w.Header().Set("X-Botan-Compiled", "hit")
+			elapsed := time.Since(timerStart)
+			w.Header().Set("X-Botan-Resolve-Time", elapsed.String())
 			w.Write(compiled)
 			return
 		}
@@ -110,5 +114,8 @@ func (h handler) index(w http.ResponseWriter, req *http.Request) {
 	w.Header().Set("Content-Type", res.ContentType)
 	w.Header().Set("X-Botan-Compiled", "miss")
 
+	elapsed := time.Since(timerStart)
+	w.Header().Set("X-Botan-Resolve-Time", elapsed.String())
+
 	_, _ = w.Write(res.Content)
 }