# UNDF: UNDF-2026-000000303
--- a/substrate/frame/staking/src/pallet/impls.rs
+++ b/substrate/frame/staking/src/pallet/impls.rs
@@ -2081,12 +2081,21 @@ impl<T: Config> sp_staking::StakingInterface for Pallet<T> {
 	fn is_exposed_in_era(who: &Self::AccountId, era: &EraIndex) -> bool {
-		// look in the non paged exposures
-		// FIXME: Can be cleaned up once non paged exposures are cleared (https://github.com/paritytech/polkadot-sdk/issues/433)
-		ErasStakers::<T>::iter_prefix(era).any(|(validator, exposures)| {
-			validator == *who || exposures.others.iter().any(|i| i.who == *who)
-		})
-			||
-		// look in the paged exposures
-		ErasStakersPaged::<T>::iter_prefix((era,)).any(|((validator, _), exposure_page)| {
-			validator == *who || exposure_page.others.iter().any(|i| i.who == *who)
-		})
+		// Fast path: check if `who` was an active validator in this era.
+		// ErasValidatorPrefs is keyed (era, validator) — O(1) storage read.
+		if ErasValidatorPrefs::<T>::contains_key(era, who) {
+			return true;
+		}
+
+		// Nominator path: still requires scanning exposure pages.
+		// FIXME: A nominator→validator reverse index would make this O(1).
+		// See https://github.com/paritytech/polkadot-sdk/issues/433
+		//
+		// look in the non-paged exposures (legacy)
+		ErasStakers::<T>::iter_prefix(era).any(|(_, exposures)| {
+			exposures.others.iter().any(|i| i.who == *who)
+		})
+			||
+		// look in the paged exposures
+		ErasStakersPaged::<T>::iter_prefix((era,)).any(|(_, exposure_page)| {
+			exposure_page.others.iter().any(|i| i.who == *who)
+		})
 	}