diff --git a/internal/etw/processors/fs_windows.go b/internal/etw/processors/fs_windows.go
index f8737868c..96a654a5b 100644
--- a/internal/etw/processors/fs_windows.go
+++ b/internal/etw/processors/fs_windows.go
@@ -20,6 +20,9 @@ package processors
 
 import (
 	"expvar"
+	"sync"
+	"time"
+
 	"github.com/rabbitstack/fibratus/pkg/config"
 	"github.com/rabbitstack/fibratus/pkg/event"
 	"github.com/rabbitstack/fibratus/pkg/event/params"
@@ -31,8 +34,6 @@ import (
 	"github.com/rabbitstack/fibratus/pkg/util/va"
 	"golang.org/x/sys/windows"
 	"golang.org/x/time/rate"
-	"sync"
-	"time"
 )
 
 var (
@@ -371,11 +372,13 @@ func (f *fsProcessor) purge() {
 
 			// evict unmatched stack traces
 			for id, q := range f.buckets {
-				for i, evt := range q {
-					if time.Since(evt.Timestamp) > time.Second*30 {
-						f.buckets[id] = append(q[:i], q[i+1:]...)
+				s := q[:0]
+				for _, evt := range q {
+					if time.Since(evt.Timestamp) <= time.Second*30 {
+						s = append(s, evt)
 					}
 				}
+				f.buckets[id] = s
 			}
 
 			f.mu.Unlock()
diff --git a/pkg/event/stackwalk.go b/pkg/event/stackwalk.go
index c54bde0d7..d785c9cca 100644
--- a/pkg/event/stackwalk.go
+++ b/pkg/event/stackwalk.go
@@ -160,8 +160,9 @@ func (s *StackwalkDecorator) Pop(e *Event) *Event {
 				if !proc.IsCreateProcess() && proc.Params.MustGetPid() != pid {
 					continue
 				}
-				s.buckets[ev.StackID()] = append(qu[:i], qu[i+1:]...)
+				qu = append(qu[:i], qu[i+1:]...)
 			}
+			s.buckets[ev.StackID()] = qu
 		}
 	}
 
@@ -209,16 +210,18 @@ func (s *StackwalkDecorator) flush() []error {
 	errs := make([]error, 0)
 
 	for id, q := range s.buckets {
-		for i, evt := range q {
+		n := q[:0]
+		for _, evt := range q {
 			if time.Since(evt.Timestamp) < maxQueueTTLPeriod {
+				n = append(n, evt)
 				continue
 			}
+
 			stackwalkFlushes.Add(1)
 			err := s.q.push(evt)
 			if err != nil {
 				errs = append(errs, err)
 			}
-			s.buckets[id] = append(q[:i], q[i+1:]...)
 			if stackwalkEnqueued.Value() > 0 {
 				stackwalkEnqueued.Add(-1)
 			}
@@ -227,6 +230,7 @@ func (s *StackwalkDecorator) flush() []error {
 			}
 			stackwalkFlushesEvents.Add(evt.Name, 1)
 		}
+		s.buckets[id] = n
 	}
 
 	return errs