diff --git a/tsdb/exemplar.go b/tsdb/exemplar.go
index 213fff5c2..7545ab9a6 100644
--- a/tsdb/exemplar.go
+++ b/tsdb/exemplar.go
@@ -37,7 +37,7 @@ const (
 
 type CircularExemplarStorage struct {
 	lock      sync.RWMutex
-	exemplars []*circularBufferEntry
+	exemplars []circularBufferEntry
 	nextIndex int
 	metrics   *ExemplarMetrics
 
@@ -121,7 +121,7 @@ func NewCircularExemplarStorage(length int64, m *ExemplarMetrics) (ExemplarStora
 		length = 0
 	}
 	c := &CircularExemplarStorage{
-		exemplars: make([]*circularBufferEntry, length),
+		exemplars: make([]circularBufferEntry, length),
 		index:     make(map[string]*indexEntry, length/estimatedExemplarsPerSeries),
 		metrics:   m,
 	}
@@ -214,12 +214,12 @@ func (ce *CircularExemplarStorage) ValidateExemplar(l labels.Labels, e exemplar.
 	// Optimize by moving the lock to be per series (& benchmark it).
 	ce.lock.RLock()
 	defer ce.lock.RUnlock()
-	return ce.validateExemplar(seriesLabels, e, false)
+	return ce.validateExemplar(ce.index[string(seriesLabels)], e, false)
 }
 
 // Not thread safe. The appended parameters tells us whether this is an external validation, or internal
 // as a result of an AddExemplar call, in which case we should update any relevant metrics.
-func (ce *CircularExemplarStorage) validateExemplar(key []byte, e exemplar.Exemplar, appended bool) error {
+func (ce *CircularExemplarStorage) validateExemplar(idx *indexEntry, e exemplar.Exemplar, appended bool) error {
 	if len(ce.exemplars) == 0 {
 		return storage.ErrExemplarsDisabled
 	}
@@ -239,8 +239,7 @@ func (ce *CircularExemplarStorage) validateExemplar(key []byte, e exemplar.Exemp
 		return err
 	}
 
-	idx, ok := ce.index[string(key)]
-	if !ok {
+	if idx == nil {
 		return nil
 	}
 
@@ -292,7 +291,7 @@ func (ce *CircularExemplarStorage) Resize(l int64) int {
 	oldBuffer := ce.exemplars
 	oldNextIndex := int64(ce.nextIndex)
 
-	ce.exemplars = make([]*circularBufferEntry, l)
+	ce.exemplars = make([]circularBufferEntry, l)
 	ce.index = make(map[string]*indexEntry, l/estimatedExemplarsPerSeries)
 	ce.nextIndex = 0
 
@@ -311,10 +310,11 @@ func (ce *CircularExemplarStorage) Resize(l int64) int {
 		// This way we don't migrate exemplars that would just be overwritten when migrating later exemplars.
 		startIndex := (oldNextIndex - count + int64(len(oldBuffer))) % int64(len(oldBuffer))
 
+		var buf [1024]byte
 		for i := int64(0); i < count; i++ {
 			idx := (startIndex + i) % int64(len(oldBuffer))
-			if entry := oldBuffer[idx]; entry != nil {
-				ce.migrate(entry)
+			if oldBuffer[idx].ref != nil {
+				ce.migrate(&oldBuffer[idx], buf[:])
 				migrated++
 			}
 		}
@@ -328,9 +328,8 @@ func (ce *CircularExemplarStorage) Resize(l int64) int {
 
 // migrate is like AddExemplar but reuses existing structs. Expected to be called in batch and requires
 // external lock and does not compute metrics.
-func (ce *CircularExemplarStorage) migrate(entry *circularBufferEntry) {
-	var buf [1024]byte
-	seriesLabels := entry.ref.seriesLabels.Bytes(buf[:])
+func (ce *CircularExemplarStorage) migrate(entry *circularBufferEntry, buf []byte) {
+	seriesLabels := entry.ref.seriesLabels.Bytes(buf[:0])
 
 	idx, ok := ce.index[string(seriesLabels)]
 	if !ok {
@@ -344,7 +343,7 @@ func (ce *CircularExemplarStorage) migrate(entry *circularBufferEntry) {
 	idx.newest = ce.nextIndex
 
 	entry.next = noExemplar
-	ce.exemplars[ce.nextIndex] = entry
+	ce.exemplars[ce.nextIndex] = *entry
 
 	ce.nextIndex = (ce.nextIndex + 1) % len(ce.exemplars)
 }
@@ -362,7 +361,8 @@ func (ce *CircularExemplarStorage) AddExemplar(l labels.Labels, e exemplar.Exemp
 	ce.lock.Lock()
 	defer ce.lock.Unlock()
 
-	err := ce.validateExemplar(seriesLabels, e, true)
+	idx, ok := ce.index[string(seriesLabels)]
+	err := ce.validateExemplar(idx, e, true)
 	if err != nil {
 		if errors.Is(err, storage.ErrDuplicateExemplar) {
 			// Duplicate exemplar, noop.
@@ -371,25 +371,23 @@ func (ce *CircularExemplarStorage) AddExemplar(l labels.Labels, e exemplar.Exemp
 		return err
 	}
 
-	_, ok := ce.index[string(seriesLabels)]
 	if !ok {
-		ce.index[string(seriesLabels)] = &indexEntry{oldest: ce.nextIndex, seriesLabels: l}
+		idx = &indexEntry{oldest: ce.nextIndex, seriesLabels: l}
+		ce.index[string(seriesLabels)] = idx
 	} else {
-		ce.exemplars[ce.index[string(seriesLabels)].newest].next = ce.nextIndex
+		ce.exemplars[idx.newest].next = ce.nextIndex
 	}
 
-	if prev := ce.exemplars[ce.nextIndex]; prev == nil {
-		ce.exemplars[ce.nextIndex] = &circularBufferEntry{}
-	} else {
+	if prev := &ce.exemplars[ce.nextIndex]; prev.ref != nil {
 		// There exists an exemplar already on this ce.nextIndex entry,
 		// drop it, to make place for others.
-		var buf [1024]byte
-		prevLabels := prev.ref.seriesLabels.Bytes(buf[:])
 		if prev.next == noExemplar {
 			// Last item for this series, remove index entry.
+			var buf [1024]byte
+			prevLabels := prev.ref.seriesLabels.Bytes(buf[:])
 			delete(ce.index, string(prevLabels))
 		} else {
-			ce.index[string(prevLabels)].oldest = prev.next
+			prev.ref.oldest = prev.next
 		}
 	}
 
@@ -397,8 +395,8 @@ func (ce *CircularExemplarStorage) AddExemplar(l labels.Labels, e exemplar.Exemp
 	// since this is the first exemplar stored for this series.
 	ce.exemplars[ce.nextIndex].next = noExemplar
 	ce.exemplars[ce.nextIndex].exemplar = e
-	ce.exemplars[ce.nextIndex].ref = ce.index[string(seriesLabels)]
-	ce.index[string(seriesLabels)].newest = ce.nextIndex
+	ce.exemplars[ce.nextIndex].ref = idx
+	idx.newest = ce.nextIndex
 
 	ce.nextIndex = (ce.nextIndex + 1) % len(ce.exemplars)
 
@@ -416,15 +414,15 @@ func (ce *CircularExemplarStorage) computeMetrics() {
 		return
 	}
 
-	if next := ce.exemplars[ce.nextIndex]; next != nil {
+	if ce.exemplars[ce.nextIndex].ref != nil {
 		ce.metrics.exemplarsInStorage.Set(float64(len(ce.exemplars)))
-		ce.metrics.lastExemplarsTs.Set(float64(next.exemplar.Ts) / 1000)
+		ce.metrics.lastExemplarsTs.Set(float64(ce.exemplars[ce.nextIndex].exemplar.Ts) / 1000)
 		return
 	}
 
 	// We did not yet fill the buffer.
 	ce.metrics.exemplarsInStorage.Set(float64(ce.nextIndex))
-	if ce.exemplars[0] != nil {
+	if ce.exemplars[0].ref != nil {
 		ce.metrics.lastExemplarsTs.Set(float64(ce.exemplars[0].exemplar.Ts) / 1000)
 	}
 }
@@ -438,7 +436,7 @@ func (ce *CircularExemplarStorage) IterateExemplars(f func(seriesLabels labels.L
 	idx := ce.nextIndex
 	l := len(ce.exemplars)
 	for i := 0; i < l; i, idx = i+1, (idx+1)%l {
-		if ce.exemplars[idx] == nil {
+		if ce.exemplars[idx].ref == nil {
 			continue
 		}
 		err := f(ce.exemplars[idx].ref.seriesLabels, ce.exemplars[idx].exemplar)
diff --git a/tsdb/exemplar_test.go b/tsdb/exemplar_test.go
index b2be22170..7723ec389 100644
--- a/tsdb/exemplar_test.go
+++ b/tsdb/exemplar_test.go
@@ -415,27 +415,29 @@ func BenchmarkAddExemplar(b *testing.B) {
 	// before adding.
 	exLabels := labels.FromStrings("trace_id", "89620921")
 
-	for _, n := range []int{10000, 100000, 1000000} {
-		b.Run(strconv.Itoa(n), func(b *testing.B) {
-			for j := 0; j < b.N; j++ {
-				b.StopTimer()
-				exs, err := NewCircularExemplarStorage(int64(n), eMetrics)
-				require.NoError(b, err)
-				es := exs.(*CircularExemplarStorage)
-				var l labels.Labels
-				b.StartTimer()
-
-				for i := 0; i < n; i++ {
-					if i%100 == 0 {
-						l = labels.FromStrings("service", strconv.Itoa(i))
-					}
-					err = es.AddExemplar(l, exemplar.Exemplar{Value: float64(i), Ts: int64(i), Labels: exLabels})
-					if err != nil {
-						require.NoError(b, err)
+	for _, capacity := range []int{1000, 10000, 100000} {
+		for _, n := range []int{10000, 100000, 1000000} {
+			b.Run(fmt.Sprintf("%d/%d", n, capacity), func(b *testing.B) {
+				for j := 0; j < b.N; j++ {
+					b.StopTimer()
+					exs, err := NewCircularExemplarStorage(int64(capacity), eMetrics)
+					require.NoError(b, err)
+					es := exs.(*CircularExemplarStorage)
+					var l labels.Labels
+					b.StartTimer()
+
+					for i := 0; i < n; i++ {
+						if i%100 == 0 {
+							l = labels.FromStrings("service", strconv.Itoa(i))
+						}
+						err = es.AddExemplar(l, exemplar.Exemplar{Value: float64(i), Ts: int64(i), Labels: exLabels})
+						if err != nil {
+							require.NoError(b, err)
+						}
 					}
 				}
-			}
-		})
+			})
+		}
 	}
 }
 
@@ -480,8 +482,11 @@ func BenchmarkResizeExemplars(b *testing.B) {
 				require.NoError(b, err)
 				es := exs.(*CircularExemplarStorage)
 
+				var l labels.Labels
 				for i := 0; i < int(float64(tc.startSize)*float64(1.5)); i++ {
-					l := labels.FromStrings("service", strconv.Itoa(i))
+					if i%100 == 0 {
+						l = labels.FromStrings("service", strconv.Itoa(i))
+					}
 
 					err = es.AddExemplar(l, exemplar.Exemplar{Value: float64(i), Ts: int64(i)})
 					if err != nil {