diff --git a/pkg/document/json/rga_tree_split.go b/pkg/document/json/rga_tree_split.go
index bc8ea7d1b..ed3cdb3ea 100644
--- a/pkg/document/json/rga_tree_split.go
+++ b/pkg/document/json/rga_tree_split.go
@@ -2,6 +2,7 @@ package json
 
 import (
 	"fmt"
+	"strconv"
 	"strings"
 
 	"github.com/yorkie-team/yorkie/internal/log"
@@ -91,7 +92,7 @@ func (t *RGATreeSplitNodeID) hasSameCreatedAt(id *RGATreeSplitNodeID) bool {
 }
 
 func (t *RGATreeSplitNodeID) key() string {
-	return fmt.Sprintf("%s:%d", t.createdAt.Key(), t.offset)
+	return t.CreatedAt().Key() + ":" + strconv.FormatUint(uint64(t.offset), 10)
 }
 
 // RGATreeSplitNodePos is the position of the text inside the node.
diff --git a/pkg/document/time/ticket.go b/pkg/document/time/ticket.go
index c0a30669f..d05367b22 100644
--- a/pkg/document/time/ticket.go
+++ b/pkg/document/time/ticket.go
@@ -19,6 +19,7 @@ package time
 import (
 	"fmt"
 	"math"
+	"strconv"
 )
 
 const (
@@ -81,12 +82,17 @@ func (t *Ticket) AnnotatedString() string {
 // Key returns the key string for this Ticket.
 func (t *Ticket) Key() string {
 	if t.actorID == nil {
-		return fmt.Sprintf("%d:%d:", t.lamport, t.delimiter)
+		return strconv.FormatUint(t.lamport, 10) +
+			":" +
+			strconv.FormatUint(uint64(t.delimiter), 10) +
+			":"
 	}
 
-	return fmt.Sprintf(
-		"%d:%d:%s", t.lamport, t.delimiter, t.actorID.String(),
-	)
+	return strconv.FormatUint(t.lamport, 10) +
+		":" +
+		strconv.FormatUint(uint64(t.delimiter), 10) +
+		":" +
+		t.actorID.String()
 }
 
 // Lamport returns the lamport value.