diff --git a/tsdb/index/postings.go b/tsdb/index/postings.go
index bfe74c323..25780e4ad 100644
--- a/tsdb/index/postings.go
+++ b/tsdb/index/postings.go
@@ -26,6 +26,7 @@ import (
 	"sync"
 
 	"github.com/bboreham/go-loser"
+	"github.com/cespare/xxhash/v2"
 
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/storage"
@@ -293,6 +294,9 @@ func (p *MemPostings) Delete(deleted map[storage.SeriesRef]struct{}, affected ma
 	p.mtx.Lock()
 	defer p.mtx.Unlock()
 
+	// Deleting label names mutates p.m map, so it should be done from a single goroutine after nobody else is reading it.
+	deleteLabelNames := make(chan string, len(p.m))
+
 	process := func(l labels.Label) {
 		orig := p.m[l.Name][l.Value]
 		repl := make([]storage.SeriesRef, 0, len(orig))
@@ -305,17 +309,46 @@ func (p *MemPostings) Delete(deleted map[storage.SeriesRef]struct{}, affected ma
 			p.m[l.Name][l.Value] = repl
 		} else {
 			delete(p.m[l.Name], l.Value)
-			// Delete the key if we removed all values.
 			if len(p.m[l.Name]) == 0 {
-				delete(p.m, l.Name)
+				// Delete the key if we removed all values.
+				deleteLabelNames <- l.Name
 			}
 		}
 	}
 
-	for l := range affected {
-		process(l)
+	// Create GOMAXPROCS workers.
+	wg := sync.WaitGroup{}
+	jobs := make([]chan labels.Label, runtime.GOMAXPROCS(0))
+	for i := range jobs {
+		jobs[i] = make(chan labels.Label, 128)
+		wg.Add(1)
+		go func(jobs chan labels.Label) {
+			defer wg.Done()
+			for l := range jobs {
+				process(l)
+			}
+		}(jobs[i])
+	}
+
+	// Process all affected labels and the allPostingsKey.
+	for l := range affected {
+		j := int(xxhash.Sum64String(l.Name) % uint64(len(jobs)))
+		jobs[j] <- l
+	}
+	j := int(xxhash.Sum64String(allPostingsKey.Name) % uint64(len(jobs)))
+	jobs[j] <- allPostingsKey
+
+	// Close jobs channels and wait all workers to finish.
+	for i := range jobs {
+		close(jobs[i])
+	}
+	wg.Wait()
+
+	// Close deleteLabelNames channel and delete the label names requested.
+	close(deleteLabelNames)
+	for name := range deleteLabelNames {
+		delete(p.m, name)
 	}
-	process(allPostingsKey)
 }
 
 // Iter calls f for each postings list. It aborts if f returns an error and returns it.
diff --git a/tsdb/index/postings_test.go b/tsdb/index/postings_test.go
index 96c9ed124..1802c9e89 100644
--- a/tsdb/index/postings_test.go
+++ b/tsdb/index/postings_test.go
@@ -1025,7 +1025,7 @@ func BenchmarkMemPostings_Delete(b *testing.B) {
 		return s
 	}
 
-	const total = 1e6
+	const total = 2e6
 	allSeries := [total]labels.Labels{}
 	nameValues := make([]string, 0, 100)
 	for i := 0; i < total; i++ {