diff --git a/promql/cache_symbols_test.go b/promql/cache_symbols_test.go
new file mode 100644
index 0000000000..d4ebf99d19
--- /dev/null
+++ b/promql/cache_symbols_test.go
@@ -0,0 +1,86 @@
+// Copyright 2021 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package promql
+
+import (
+	"context"
+	"fmt"
+	"github.com/go-kit/log"
+	"github.com/go-kit/log/level"
+	"github.com/prometheus/prometheus/tsdb"
+	"go.opentelemetry.io/otel"
+	"os"
+	"testing"
+	"time"
+)
+
+func BenchmarkCountSingleInstance(b *testing.B) {
+	benchmarkQuery("count(bid_request_count{instance='vad-gp-bac12-1:11108'})", b)
+}
+
+func BenchmarkCountAll(b *testing.B) {
+	benchmarkQuery("count(bid_request_count)", b)
+}
+
+func BenchmarkCountSingleInstanceOver1h(b *testing.B) {
+	benchmarkQuery("count(count_over_time(bid_request_count{instance='vad-gp-bac12-1:11108'}[1h]))", b)
+}
+
+func BenchmarkCountAllOver1h(b *testing.B) {
+	benchmarkQuery("count(count_over_time(bid_request_count[1h]))", b)
+}
+
+func benchmarkQuery(query string, b *testing.B) {
+	// Open a TSDB for reading and/or writing.
+	l := log.NewLogfmtLogger(log.NewSyncWriter(os.Stderr))
+	l = level.NewFilter(l, level.AllowError())
+	// TSDB contains a single production block, containing a high cardinality series (~150K)
+	db, err := tsdb.Open("/temp/test-tsdb", l, nil, tsdb.DefaultOptions(), nil)
+	noErr(err)
+
+	// Create engine for querying
+	otel.Tracer("name").Start(context.Background(), "Run")
+	eng := NewEngine(EngineOpts{
+		Logger:             l,
+		Reg:                nil,
+		MaxSamples:         50000000,
+		Timeout:            60 * time.Second,
+		EnablePerStepStats: true,
+	})
+	noErr(err)
+
+	for n := 0; n < b.N; n++ {
+		q, err := eng.NewInstantQuery(context.Background(), db, &PrometheusQueryOpts{}, query, time.UnixMilli(1688922000001))
+		noErr(err)
+		q.Stats().Samples.EnablePerStepStats = true
+		b.StartTimer()
+		q.Exec(context.Background())
+		b.StopTimer()
+
+		if n == 0 {
+			fmt.Printf("Peak samples: %v, Total samples: %v", q.Stats().Samples.PeakSamples, q.Stats().Samples.TotalSamples)
+			fmt.Println()
+		}
+	}
+
+	// Clean up any last resources when done.
+	err = db.Close()
+	noErr(err)
+}
+
+func noErr(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
diff --git a/tsdb/index/index.go b/tsdb/index/index.go
index 911b1a6ecc..a8bdd66e38 100644
--- a/tsdb/index/index.go
+++ b/tsdb/index/index.go
@@ -1477,7 +1477,11 @@ func (r *Reader) lookupSymbol(ctx context.Context, o uint32) (string, error) {
 	if s, ok := r.nameSymbols[o]; ok {
 		return s, nil
 	}
-	return r.symbols.Lookup(o)
+	s, err := r.symbols.Lookup(o)
+	if err == nil {
+		r.nameSymbols[o] = s
+	}
+	return s, err
 }
 
 // Symbols returns an iterator over the symbols that exist within the index.