diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index 453c3695a481..faf85efa31a0 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -76,6 +76,8 @@ Optimizations
 
 * GITHUB#11857, GITHUB#11859, GITHUB#11893, GITHUB#11909: Hunspell: improved suggestion performance (Peter Gromov)
 
+* GITHUB#12328: Optimize ConjunctionDISI.createConjunction (Armin Braun)
+
 Bug Fixes
 ---------------------
 
diff --git a/lucene/core/src/java/org/apache/lucene/search/ConjunctionDISI.java b/lucene/core/src/java/org/apache/lucene/search/ConjunctionDISI.java
index b70224f1ec50..4fc74b4f0871 100644
--- a/lucene/core/src/java/org/apache/lucene/search/ConjunctionDISI.java
+++ b/lucene/core/src/java/org/apache/lucene/search/ConjunctionDISI.java
@@ -20,7 +20,6 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.Comparator;
 import java.util.List;
 import org.apache.lucene.util.ArrayUtil;
 import org.apache.lucene.util.BitSet;
@@ -99,24 +98,26 @@ static DocIdSetIterator createConjunction(
         allIterators.size() > 0
             ? allIterators.get(0).docID()
             : twoPhaseIterators.get(0).approximation.docID();
-    boolean iteratorsOnTheSameDoc = allIterators.stream().allMatch(it -> it.docID() == curDoc);
-    iteratorsOnTheSameDoc =
-        iteratorsOnTheSameDoc
-            && twoPhaseIterators.stream().allMatch(it -> it.approximation().docID() == curDoc);
-    if (iteratorsOnTheSameDoc == false) {
-      throw new IllegalArgumentException(
-          "Sub-iterators of ConjunctionDISI are not on the same document!");
+    long minCost = Long.MAX_VALUE;
+    for (DocIdSetIterator allIterator : allIterators) {
+      if (allIterator.docID() != curDoc) {
+        throwSubIteratorsNotOnSameDocument();
+      }
+      minCost = Math.min(allIterator.cost(), minCost);
+    }
+    for (TwoPhaseIterator it : twoPhaseIterators) {
+      if (it.approximation().docID() != curDoc) {
+        throwSubIteratorsNotOnSameDocument();
+      }
     }
-
-    long minCost = allIterators.stream().mapToLong(DocIdSetIterator::cost).min().getAsLong();
     List<BitSetIterator> bitSetIterators = new ArrayList<>();
     List<DocIdSetIterator> iterators = new ArrayList<>();
     for (DocIdSetIterator iterator : allIterators) {
-      if (iterator.cost() > minCost && iterator instanceof BitSetIterator) {
+      if (iterator instanceof BitSetIterator bitSetIterator && bitSetIterator.cost() > minCost) {
         // we put all bitset iterators into bitSetIterators
         // except if they have the minimum cost, since we need
         // them to lead the iteration in that case
-        bitSetIterators.add((BitSetIterator) iterator);
+        bitSetIterators.add(bitSetIterator);
       } else {
         iterators.add(iterator);
       }
@@ -142,6 +143,11 @@ static DocIdSetIterator createConjunction(
     return disi;
   }
 
+  private static void throwSubIteratorsNotOnSameDocument() {
+    throw new IllegalArgumentException(
+        "Sub-iterators of ConjunctionDISI are not on the same document!");
+  }
+
   final DocIdSetIterator lead1, lead2;
   final DocIdSetIterator[] others;
 
@@ -150,14 +156,7 @@ private ConjunctionDISI(List<? extends DocIdSetIterator> iterators) {
 
     // Sort the array the first time to allow the least frequent DocsEnum to
     // lead the matching.
-    CollectionUtil.timSort(
-        iterators,
-        new Comparator<DocIdSetIterator>() {
-          @Override
-          public int compare(DocIdSetIterator o1, DocIdSetIterator o2) {
-            return Long.compare(o1.cost(), o2.cost());
-          }
-        });
+    CollectionUtil.timSort(iterators, (o1, o2) -> Long.compare(o1.cost(), o2.cost()));
     lead1 = iterators.get(0);
     lead2 = iterators.get(1);
     others = iterators.subList(2, iterators.size()).toArray(new DocIdSetIterator[0]);
@@ -326,13 +325,7 @@ private ConjunctionTwoPhaseIterator(
       assert twoPhaseIterators.size() > 0;
 
       CollectionUtil.timSort(
-          twoPhaseIterators,
-          new Comparator<TwoPhaseIterator>() {
-            @Override
-            public int compare(TwoPhaseIterator o1, TwoPhaseIterator o2) {
-              return Float.compare(o1.matchCost(), o2.matchCost());
-            }
-          });
+          twoPhaseIterators, (o1, o2) -> Float.compare(o1.matchCost(), o2.matchCost()));
 
       this.twoPhaseIterators =
           twoPhaseIterators.toArray(new TwoPhaseIterator[twoPhaseIterators.size()]);