diff --git a/backend/internal/assets/cacher/cacher.go b/backend/internal/assets/cacher/cacher.go
index fd7fe1e70..619c28c7c 100644
--- a/backend/internal/assets/cacher/cacher.go
+++ b/backend/internal/assets/cacher/cacher.go
@@ -73,7 +73,8 @@ func (c *cacher) cacheURL(requestURL string, sessionID uint64, depth byte, urlCo
 		return
 	}
 	c.timeoutMap.add(cachePath)
-	if c.s3.Exists(cachePath) {
+	crTime := c.s3.GetCreationTime(cachePath)
+	if crTime != nil && crTime.After(time.Now().Add(-MAX_STORAGE_TIME)) { // recently uploaded
 		return
 	}
 
diff --git a/backend/pkg/storage/s3.go b/backend/pkg/storage/s3.go
index 67ebaaf4f..2e97673d3 100644
--- a/backend/pkg/storage/s3.go
+++ b/backend/pkg/storage/s3.go
@@ -6,6 +6,7 @@ import (
 	"os"
 	"sort"
 	"strconv"
+	"time"
 
 	_s3 "github.com/aws/aws-sdk-go/service/s3"
 	"github.com/aws/aws-sdk-go/service/s3/s3manager"
@@ -71,6 +72,17 @@ func (s3 *S3) Exists(key string) bool {
 	return false
 }
 
+func (s3 *S3) GetCreationTime(key string) *time.Time {
+	ans, err := s3.svc.HeadObject(&_s3.HeadObjectInput{
+		Bucket: s3.bucket,
+		Key:    &key,
+	})
+	if err != nil {
+		return nil
+	}
+	return ans.LastModified
+}
+
 const MAX_RETURNING_COUNT = 40
 
 func (s3 *S3) GetFrequentlyUsedKeys(projectID uint64) ([]string, error) {
diff --git a/backend/pkg/url/assets/url.go b/backend/pkg/url/assets/url.go
index adb26e0aa..83cdd5ac1 100644
--- a/backend/pkg/url/assets/url.go
+++ b/backend/pkg/url/assets/url.go
@@ -14,7 +14,7 @@ func getSessionKey(sessionID uint64) string {
 	return strconv.FormatUint(
 		uint64(time.UnixMilli(
 			int64(flakeid.ExtractTimestamp(sessionID)),
-		).Weekday()),
+		).Day()),
 		10,
 	)
 }