diff --git a/internal/transport/http_util.go b/internal/transport/http_util.go
index d632dc4e812..2c601a864d9 100644
--- a/internal/transport/http_util.go
+++ b/internal/transport/http_util.go
@@ -20,7 +20,6 @@ package transport
 
 import (
 	"bufio"
-	"bytes"
 	"encoding/base64"
 	"fmt"
 	"io"
@@ -251,13 +250,13 @@ func encodeGrpcMessage(msg string) string {
 }
 
 func encodeGrpcMessageUnchecked(msg string) string {
-	var buf bytes.Buffer
+	var sb strings.Builder
 	for len(msg) > 0 {
 		r, size := utf8.DecodeRuneInString(msg)
 		for _, b := range []byte(string(r)) {
 			if size > 1 {
 				// If size > 1, r is not ascii. Always do percent encoding.
-				buf.WriteString(fmt.Sprintf("%%%02X", b))
+				fmt.Fprintf(&sb, "%%%02X", b)
 				continue
 			}
 
@@ -266,14 +265,14 @@ func encodeGrpcMessageUnchecked(msg string) string {
 			//
 			// fmt.Sprintf("%%%02X", utf8.RuneError) gives "%FFFD".
 			if b >= spaceByte && b <= tildeByte && b != percentByte {
-				buf.WriteByte(b)
+				sb.WriteByte(b)
 			} else {
-				buf.WriteString(fmt.Sprintf("%%%02X", b))
+				fmt.Fprintf(&sb, "%%%02X", b)
 			}
 		}
 		msg = msg[size:]
 	}
-	return buf.String()
+	return sb.String()
 }
 
 // decodeGrpcMessage decodes the msg encoded by encodeGrpcMessage.
@@ -291,23 +290,23 @@ func decodeGrpcMessage(msg string) string {
 }
 
 func decodeGrpcMessageUnchecked(msg string) string {
-	var buf bytes.Buffer
+	var sb strings.Builder
 	lenMsg := len(msg)
 	for i := 0; i < lenMsg; i++ {
 		c := msg[i]
 		if c == percentByte && i+2 < lenMsg {
 			parsed, err := strconv.ParseUint(msg[i+1:i+3], 16, 8)
 			if err != nil {
-				buf.WriteByte(c)
+				sb.WriteByte(c)
 			} else {
-				buf.WriteByte(byte(parsed))
+				sb.WriteByte(byte(parsed))
 				i += 2
 			}
 		} else {
-			buf.WriteByte(c)
+			sb.WriteByte(c)
 		}
 	}
-	return buf.String()
+	return sb.String()
 }
 
 type bufWriter struct {
diff --git a/internal/transport/http_util_test.go b/internal/transport/http_util_test.go
index bbd53180471..cc7807670b6 100644
--- a/internal/transport/http_util_test.go
+++ b/internal/transport/http_util_test.go
@@ -214,3 +214,27 @@ func (s) TestParseDialTarget(t *testing.T) {
 		}
 	}
 }
+
+func BenchmarkDecodeGrpcMessage(b *testing.B) {
+	input := "Hello, %E4%B8%96%E7%95%8C"
+	want := "Hello, 世界"
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		got := decodeGrpcMessage(input)
+		if got != want {
+			b.Fatalf("decodeGrpcMessage(%q) = %s, want %s", input, got, want)
+		}
+	}
+}
+
+func BenchmarkEncodeGrpcMessage(b *testing.B) {
+	input := "Hello, 世界"
+	want := "Hello, %E4%B8%96%E7%95%8C"
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		got := encodeGrpcMessage(input)
+		if got != want {
+			b.Fatalf("encodeGrpcMessage(%q) = %s, want %s", input, got, want)
+		}
+	}
+}