diff --git a/src/stream/src/executor/over_window/over_partition.rs b/src/stream/src/executor/over_window/over_partition.rs
index 8ce4cf1968ef2..1d308d4007515 100644
--- a/src/stream/src/executor/over_window/over_partition.rs
+++ b/src/stream/src/executor/over_window/over_partition.rs
@@ -88,25 +88,25 @@ pub(super) fn shrink_partition_cache(
 
             let mut cursor = range_cache.inner().upper_bound(Bound::Excluded(&ck_start));
             for _ in 0..MAGIC_JITTER_PREVENTION {
-                if cursor.key().is_none() {
+                if cursor.prev().is_none() {
                     break;
                 }
-                cursor.move_prev();
             }
             let start = cursor
-                .key()
+                .peek_prev()
+                .map(|(k, _)| k)
                 .unwrap_or_else(|| range_cache.first_key_value().unwrap().0)
                 .clone();
 
-            let mut cursor = range_cache.inner().lower_bound(Bound::Excluded(&ck_end));
+            let mut cursor = range_cache.inner().lower_bound(Bound::Included(&ck_start));
             for _ in 0..MAGIC_JITTER_PREVENTION {
-                if cursor.key().is_none() {
+                if cursor.next().is_none() {
                     break;
                 }
-                cursor.move_next();
             }
             let end = cursor
-                .key()
+                .peek_next()
+                .map(|(k, _)| k)
                 .unwrap_or_else(|| range_cache.last_key_value().unwrap().0)
                 .clone();
 
@@ -125,27 +125,27 @@ pub(super) fn shrink_partition_cache(
                 let mut cursor = range_cache.inner().upper_bound(Bound::Excluded(&ck_start));
                 // go back for at most `MAGIC_JITTER_PREVENTION` entries
                 for _ in 0..MAGIC_JITTER_PREVENTION {
-                    if cursor.key().is_none() {
+                    if cursor.prev().is_none() {
                         break;
                     }
-                    cursor.move_prev();
                     capacity_remain -= 1;
                 }
                 let start = cursor
-                    .key()
+                    .peek_prev()
+                    .map(|(k, _)| k)
                     .unwrap_or_else(|| range_cache.first_key_value().unwrap().0)
                     .clone();
 
                 let mut cursor = range_cache.inner().lower_bound(Bound::Included(&ck_start));
                 // go forward for at most `capacity_remain` entries
                 for _ in 0..capacity_remain {
-                    if cursor.key().is_none() {
+                    if cursor.next().is_none() {
                         break;
                     }
-                    cursor.move_next();
                 }
                 let end = cursor
-                    .key()
+                    .peek_next()
+                    .map(|(k, _)| k)
                     .unwrap_or_else(|| range_cache.last_key_value().unwrap().0)
                     .clone();
 
@@ -165,27 +165,27 @@ pub(super) fn shrink_partition_cache(
                 let mut cursor = range_cache.inner().lower_bound(Bound::Excluded(&ck_end));
                 // go forward for at most `MAGIC_JITTER_PREVENTION` entries
                 for _ in 0..MAGIC_JITTER_PREVENTION {
-                    if cursor.key().is_none() {
+                    if cursor.next().is_none() {
                         break;
                     }
-                    cursor.move_next();
                     capacity_remain -= 1;
                 }
                 let end = cursor
-                    .key()
+                    .peek_next()
+                    .map(|(k, _)| k)
                     .unwrap_or_else(|| range_cache.last_key_value().unwrap().0)
                     .clone();
 
                 let mut cursor = range_cache.inner().upper_bound(Bound::Included(&ck_end));
                 // go back for at most `capacity_remain` entries
                 for _ in 0..capacity_remain {
-                    if cursor.key().is_none() {
+                    if cursor.prev().is_none() {
                         break;
                     }
-                    cursor.move_prev();
                 }
                 let start = cursor
-                    .key()
+                    .peek_prev()
+                    .map(|(k, _)| k)
                     .unwrap_or_else(|| range_cache.first_key_value().unwrap().0)
                     .clone();