# UNDF: UNDF-2026-000000063
diff --git a/source/extensions/retry/host/previous_hosts/previous_hosts.h b/source/extensions/retry/host/previous_hosts/previous_hosts.h
index 1234567..abcdef0 100644
--- a/source/extensions/retry/host/previous_hosts/previous_hosts.h
+++ b/source/extensions/retry/host/previous_hosts/previous_hosts.h
@@ -1,18 +1,20 @@
 #pragma once

 #include "envoy/upstream/retry.h"
 #include "envoy/upstream/upstream.h"
+#include "absl/container/flat_hash_set.h"

 namespace Envoy {
 class PreviousHostsRetryPredicate : public Upstream::RetryHostPredicate {
 public:
   bool shouldSelectAnotherHost(const Upstream::Host& candidate_host) override {
-    return std::find(attempted_hosts_.begin(), attempted_hosts_.end(), &candidate_host) !=
-           attempted_hosts_.end();
+    return attempted_hosts_.contains(&candidate_host);
   }
   void onHostAttempted(Upstream::HostDescriptionConstSharedPtr attempted_host) override {
-    attempted_hosts_.emplace_back(attempted_host.get());
+    attempted_hosts_.insert(attempted_host.get());
   }

 private:
-  std::vector<Upstream::HostDescription const*> attempted_hosts_;
+  absl::flat_hash_set<Upstream::HostDescription const*> attempted_hosts_;
 };
 } // namespace Envoy