diff --git a/lib/mergeset/block_stream_reader_test.go b/lib/mergeset/block_stream_reader_test.go
index c9175549d..acc7ec80c 100644
--- a/lib/mergeset/block_stream_reader_test.go
+++ b/lib/mergeset/block_stream_reader_test.go
@@ -2,16 +2,18 @@ package mergeset
 
 import (
 	"fmt"
+	"math/rand"
 	"sort"
 	"testing"
 	"time"
 )
 
 func TestBlockStreamReaderReadFromInmemoryPart(t *testing.T) {
+	r := rand.New(rand.NewSource(1))
 	var items []string
 	var ib inmemoryBlock
 	for i := 0; i < 100; i++ {
-		item := getRandomBytes()
+		item := getRandomBytes(r)
 		if !ib.Add(item) {
 			break
 		}
diff --git a/lib/mergeset/encoding_test.go b/lib/mergeset/encoding_test.go
index 8e6ecffd0..fc658ab5b 100644
--- a/lib/mergeset/encoding_test.go
+++ b/lib/mergeset/encoding_test.go
@@ -4,7 +4,6 @@ import (
 	"math/rand"
 	"reflect"
 	"sort"
-	"sync"
 	"testing"
 	"testing/quick"
 
@@ -33,6 +32,8 @@ func TestCommonPrefixLen(t *testing.T) {
 }
 
 func TestInmemoryBlockAdd(t *testing.T) {
+	r := rand.New(rand.NewSource(1))
+
 	var ib inmemoryBlock
 
 	for i := 0; i < 30; i++ {
@@ -42,7 +43,7 @@ func TestInmemoryBlockAdd(t *testing.T) {
 
 		// Fill ib.
 		for j := 0; j < i*100+1; j++ {
-			s := getRandomBytes()
+			s := getRandomBytes(r)
 			if !ib.Add(s) {
 				// ib is full.
 				break
@@ -69,6 +70,7 @@ func TestInmemoryBlockAdd(t *testing.T) {
 }
 
 func TestInmemoryBlockSort(t *testing.T) {
+	r := rand.New(rand.NewSource(1))
 	var ib inmemoryBlock
 
 	for i := 0; i < 100; i++ {
@@ -77,8 +79,8 @@ func TestInmemoryBlockSort(t *testing.T) {
 		ib.Reset()
 
 		// Fill ib.
-		for j := 0; j < rand.Intn(1500); j++ {
-			s := getRandomBytes()
+		for j := 0; j < r.Intn(1500); j++ {
+			s := getRandomBytes(r)
 			if !ib.Add(s) {
 				// ib is full.
 				break
@@ -109,6 +111,7 @@ func TestInmemoryBlockSort(t *testing.T) {
 }
 
 func TestInmemoryBlockMarshalUnmarshal(t *testing.T) {
+	r := rand.New(rand.NewSource(1))
 	var ib, ib2 inmemoryBlock
 	var sb storageBlock
 	var firstItem, commonPrefix []byte
@@ -121,9 +124,9 @@ func TestInmemoryBlockMarshalUnmarshal(t *testing.T) {
 		ib.Reset()
 
 		// Fill ib.
-		itemsCount := 2 * (rand.Intn(i+1) + 1)
+		itemsCount := 2 * (r.Intn(i+1) + 1)
 		for j := 0; j < itemsCount/2; j++ {
-			s := getRandomBytes()
+			s := getRandomBytes(r)
 			s = []byte("prefix " + string(s))
 			if !ib.Add(s) {
 				// ib is full.
@@ -132,7 +135,7 @@ func TestInmemoryBlockMarshalUnmarshal(t *testing.T) {
 			items = append(items, string(s))
 			totalLen += len(s)
 
-			s = getRandomBytes()
+			s = getRandomBytes(r)
 			if !ib.Add(s) {
 				// ib is full
 				break
@@ -186,10 +189,8 @@ func TestInmemoryBlockMarshalUnmarshal(t *testing.T) {
 	}
 }
 
-func getRandomBytes() []byte {
-	rndLock.Lock()
-	iv, ok := quick.Value(bytesType, rnd)
-	rndLock.Unlock()
+func getRandomBytes(r *rand.Rand) []byte {
+	iv, ok := quick.Value(bytesType, r)
 	if !ok {
 		logger.Panicf("error in quick.Value when generating random string")
 	}
@@ -197,8 +198,3 @@ func getRandomBytes() []byte {
 }
 
 var bytesType = reflect.TypeOf([]byte(nil))
-
-var (
-	rnd     = rand.New(rand.NewSource(1))
-	rndLock sync.Mutex
-)
diff --git a/lib/mergeset/merge_test.go b/lib/mergeset/merge_test.go
index 6ba874a67..2298a1991 100644
--- a/lib/mergeset/merge_test.go
+++ b/lib/mergeset/merge_test.go
@@ -23,8 +23,10 @@ func TestMergeBlockStreams(t *testing.T) {
 }
 
 func TestMultilevelMerge(t *testing.T) {
+	r := rand.New(rand.NewSource(1))
+
 	// Prepare blocks to merge.
-	bsrs, items := newTestInmemoryBlockStreamReaders(10, 4000)
+	bsrs, items := newTestInmemoryBlockStreamReaders(r, 10, 4000)
 	var itemsMerged uint64
 
 	// First level merge
@@ -70,7 +72,8 @@ func TestMultilevelMerge(t *testing.T) {
 }
 
 func TestMergeForciblyStop(t *testing.T) {
-	bsrs, _ := newTestInmemoryBlockStreamReaders(20, 4000)
+	r := rand.New(rand.NewSource(1))
+	bsrs, _ := newTestInmemoryBlockStreamReaders(r, 20, 4000)
 	var dstIP inmemoryPart
 	var bsw blockStreamWriter
 	bsw.InitFromInmemoryPart(&dstIP, 1)
@@ -88,16 +91,18 @@ func TestMergeForciblyStop(t *testing.T) {
 func testMergeBlockStreams(t *testing.T, blocksToMerge, maxItemsPerBlock int) {
 	t.Helper()
 
-	if err := testMergeBlockStreamsSerial(blocksToMerge, maxItemsPerBlock); err != nil {
+	r := rand.New(rand.NewSource(1))
+	if err := testMergeBlockStreamsSerial(r, blocksToMerge, maxItemsPerBlock); err != nil {
 		t.Fatalf("unexpected error in serial test: %s", err)
 	}
 
 	const concurrency = 3
 	ch := make(chan error, concurrency)
 	for i := 0; i < concurrency; i++ {
-		go func() {
-			ch <- testMergeBlockStreamsSerial(blocksToMerge, maxItemsPerBlock)
-		}()
+		go func(n int) {
+			rLocal := rand.New(rand.NewSource(int64(n)))
+			ch <- testMergeBlockStreamsSerial(rLocal, blocksToMerge, maxItemsPerBlock)
+		}(i)
 	}
 
 	for i := 0; i < concurrency; i++ {
@@ -112,9 +117,9 @@ func testMergeBlockStreams(t *testing.T, blocksToMerge, maxItemsPerBlock int) {
 	}
 }
 
-func testMergeBlockStreamsSerial(blocksToMerge, maxItemsPerBlock int) error {
+func testMergeBlockStreamsSerial(r *rand.Rand, blocksToMerge, maxItemsPerBlock int) error {
 	// Prepare blocks to merge.
-	bsrs, items := newTestInmemoryBlockStreamReaders(blocksToMerge, maxItemsPerBlock)
+	bsrs, items := newTestInmemoryBlockStreamReaders(r, blocksToMerge, maxItemsPerBlock)
 
 	// Merge blocks.
 	var itemsMerged uint64
@@ -175,14 +180,14 @@ func testCheckItems(dstIP *inmemoryPart, items []string) error {
 	return nil
 }
 
-func newTestInmemoryBlockStreamReaders(blocksCount, maxItemsPerBlock int) ([]*blockStreamReader, []string) {
+func newTestInmemoryBlockStreamReaders(r *rand.Rand, blocksCount, maxItemsPerBlock int) ([]*blockStreamReader, []string) {
 	var items []string
 	var bsrs []*blockStreamReader
 	for i := 0; i < blocksCount; i++ {
 		var ib inmemoryBlock
-		itemsPerBlock := rand.Intn(maxItemsPerBlock) + 1
+		itemsPerBlock := r.Intn(maxItemsPerBlock) + 1
 		for j := 0; j < itemsPerBlock; j++ {
-			item := getRandomBytes()
+			item := getRandomBytes(r)
 			if !ib.Add(item) {
 				break
 			}
diff --git a/lib/mergeset/part_search_test.go b/lib/mergeset/part_search_test.go
index c042d44ac..72434a402 100644
--- a/lib/mergeset/part_search_test.go
+++ b/lib/mergeset/part_search_test.go
@@ -9,13 +9,14 @@ import (
 )
 
 func TestPartSearch(t *testing.T) {
-	p, items, err := newTestPart(10, 4000)
+	r := rand.New(rand.NewSource(1))
+	p, items, err := newTestPart(r, 10, 4000)
 	if err != nil {
 		t.Fatalf("cannot create test part: %s", err)
 	}
 
 	t.Run("serial", func(t *testing.T) {
-		if err := testPartSearchSerial(p, items); err != nil {
+		if err := testPartSearchSerial(r, p, items); err != nil {
 			t.Fatalf("error in serial part search test: %s", err)
 		}
 	})
@@ -31,9 +32,10 @@ func testPartSearchConcurrent(p *part, items []string) error {
 	const goroutinesCount = 5
 	ch := make(chan error, goroutinesCount)
 	for i := 0; i < goroutinesCount; i++ {
-		go func() {
-			ch <- testPartSearchSerial(p, items)
-		}()
+		go func(n int) {
+			rLocal := rand.New(rand.NewSource(int64(n)))
+			ch <- testPartSearchSerial(rLocal, p, items)
+		}(i)
 	}
 	for i := 0; i < goroutinesCount; i++ {
 		select {
@@ -48,7 +50,7 @@ func testPartSearchConcurrent(p *part, items []string) error {
 	return nil
 }
 
-func testPartSearchSerial(p *part, items []string) error {
+func testPartSearchSerial(r *rand.Rand, p *part, items []string) error {
 	var ps partSearch
 
 	ps.Init(p)
@@ -88,7 +90,7 @@ func testPartSearchSerial(p *part, items []string) error {
 
 	// Search for inner items
 	for loop := 0; loop < 100; loop++ {
-		idx := rand.Intn(len(items))
+		idx := r.Intn(len(items))
 		k = append(k[:0], items[idx]...)
 		ps.Seek(k)
 		n := sort.Search(len(items), func(i int) bool {
@@ -143,8 +145,8 @@ func testPartSearchSerial(p *part, items []string) error {
 	return nil
 }
 
-func newTestPart(blocksCount, maxItemsPerBlock int) (*part, []string, error) {
-	bsrs, items := newTestInmemoryBlockStreamReaders(blocksCount, maxItemsPerBlock)
+func newTestPart(r *rand.Rand, blocksCount, maxItemsPerBlock int) (*part, []string, error) {
+	bsrs, items := newTestInmemoryBlockStreamReaders(r, blocksCount, maxItemsPerBlock)
 
 	var itemsMerged uint64
 	var ip inmemoryPart
diff --git a/lib/mergeset/table_search_test.go b/lib/mergeset/table_search_test.go
index f0ec1f888..181daa38b 100644
--- a/lib/mergeset/table_search_test.go
+++ b/lib/mergeset/table_search_test.go
@@ -27,7 +27,8 @@ func TestTableSearchSerial(t *testing.T) {
 	const itemsCount = 1e5
 
 	items := func() []string {
-		tb, items, err := newTestTable(path, itemsCount)
+		r := rand.New(rand.NewSource(1))
+		tb, items, err := newTestTable(r, path, itemsCount)
 		if err != nil {
 			t.Fatalf("cannot create test table: %s", err)
 		}
@@ -63,7 +64,8 @@ func TestTableSearchConcurrent(t *testing.T) {
 
 	const itemsCount = 1e5
 	items := func() []string {
-		tb, items, err := newTestTable(path, itemsCount)
+		r := rand.New(rand.NewSource(2))
+		tb, items, err := newTestTable(r, path, itemsCount)
 		if err != nil {
 			t.Fatalf("cannot create test table: %s", err)
 		}
@@ -148,7 +150,7 @@ func testTableSearchSerial(tb *Table, items []string) error {
 	return nil
 }
 
-func newTestTable(path string, itemsCount int) (*Table, []string, error) {
+func newTestTable(r *rand.Rand, path string, itemsCount int) (*Table, []string, error) {
 	var flushes uint64
 	flushCallback := func() {
 		atomic.AddUint64(&flushes, 1)
@@ -160,7 +162,7 @@ func newTestTable(path string, itemsCount int) (*Table, []string, error) {
 	}
 	items := make([]string, itemsCount)
 	for i := 0; i < itemsCount; i++ {
-		item := fmt.Sprintf("%d:%d", rand.Intn(1e9), i)
+		item := fmt.Sprintf("%d:%d", r.Intn(1e9), i)
 		tb.AddItems([][]byte{[]byte(item)})
 		items[i] = item
 	}
diff --git a/lib/mergeset/table_search_timing_test.go b/lib/mergeset/table_search_timing_test.go
index 555fd8578..12fbcb7ee 100644
--- a/lib/mergeset/table_search_timing_test.go
+++ b/lib/mergeset/table_search_timing_test.go
@@ -17,6 +17,8 @@ func BenchmarkTableSearch(b *testing.B) {
 }
 
 func benchmarkTableSearch(b *testing.B, itemsCount int) {
+	r := rand.New(rand.NewSource(1))
+
 	path := fmt.Sprintf("BenchmarkTableSearch-%d", itemsCount)
 	if err := os.RemoveAll(path); err != nil {
 		b.Fatalf("cannot remove %q: %s", path, err)
@@ -25,7 +27,7 @@ func benchmarkTableSearch(b *testing.B, itemsCount int) {
 		_ = os.RemoveAll(path)
 	}()
 
-	tb, items, err := newTestTable(path, itemsCount)
+	tb, items, err := newTestTable(r, path, itemsCount)
 	if err != nil {
 		panic(fmt.Errorf("cannot create test table at %q with %d items: %w", path, itemsCount, err))
 	}
@@ -52,7 +54,7 @@ func benchmarkTableSearch(b *testing.B, itemsCount int) {
 	})
 
 	randKeys := append([][]byte{}, keys...)
-	rand.Shuffle(len(randKeys), func(i, j int) {
+	r.Shuffle(len(randKeys), func(i, j int) {
 		randKeys[i], randKeys[j] = randKeys[j], randKeys[i]
 	})
 	b.Run("random-keys-exact", func(b *testing.B) {
@@ -81,11 +83,12 @@ func benchmarkTableSearchKeysExt(b *testing.B, tb *Table, keys [][]byte, stripSu
 	b.ReportAllocs()
 	b.SetBytes(int64(searchKeysCount * rowsToScan))
 	b.RunParallel(func(pb *testing.PB) {
+		r := rand.New(rand.NewSource(1))
 		var ts TableSearch
 		ts.Init(tb)
 		defer ts.MustClose()
 		for pb.Next() {
-			startIdx := rand.Intn(len(keys) - searchKeysCount)
+			startIdx := r.Intn(len(keys) - searchKeysCount)
 			searchKeys := keys[startIdx : startIdx+searchKeysCount]
 			for i, key := range searchKeys {
 				searchKey := key
diff --git a/lib/mergeset/table_test.go b/lib/mergeset/table_test.go
index eff20bcb5..6f3de5dee 100644
--- a/lib/mergeset/table_test.go
+++ b/lib/mergeset/table_test.go
@@ -3,6 +3,7 @@ package mergeset
 import (
 	"bytes"
 	"fmt"
+	"math/rand"
 	"os"
 	"sync"
 	"sync/atomic"
@@ -61,6 +62,7 @@ func TestTableOpenMultipleTimes(t *testing.T) {
 }
 
 func TestTableAddItemsSerial(t *testing.T) {
+	r := rand.New(rand.NewSource(1))
 	const path = "TestTableAddItemsSerial"
 	if err := os.RemoveAll(path); err != nil {
 		t.Fatalf("cannot remove %q: %s", path, err)
@@ -80,7 +82,7 @@ func TestTableAddItemsSerial(t *testing.T) {
 	}
 
 	const itemsCount = 10e3
-	testAddItemsSerial(tb, itemsCount)
+	testAddItemsSerial(r, tb, itemsCount)
 
 	// Verify items count after pending items flush.
 	tb.DebugFlush()
@@ -105,16 +107,16 @@ func TestTableAddItemsSerial(t *testing.T) {
 		t.Fatalf("cannot open %q: %s", path, err)
 	}
 	const moreItemsCount = itemsCount * 3
-	testAddItemsSerial(tb, moreItemsCount)
+	testAddItemsSerial(r, tb, moreItemsCount)
 	tb.MustClose()
 
 	// Re-open the table and verify itemsCount again.
 	testReopenTable(t, path, itemsCount+moreItemsCount)
 }
 
-func testAddItemsSerial(tb *Table, itemsCount int) {
+func testAddItemsSerial(r *rand.Rand, tb *Table, itemsCount int) {
 	for i := 0; i < itemsCount; i++ {
-		item := getRandomBytes()
+		item := getRandomBytes(r)
 		if len(item) > maxInmemoryBlockSize {
 			item = item[:maxInmemoryBlockSize]
 		}
@@ -263,16 +265,17 @@ func testAddItemsConcurrent(tb *Table, itemsCount int) {
 	var wg sync.WaitGroup
 	for i := 0; i < goroutinesCount; i++ {
 		wg.Add(1)
-		go func() {
+		go func(n int) {
 			defer wg.Done()
+			r := rand.New(rand.NewSource(int64(n)))
 			for range workCh {
-				item := getRandomBytes()
+				item := getRandomBytes(r)
 				if len(item) > maxInmemoryBlockSize {
 					item = item[:maxInmemoryBlockSize]
 				}
 				tb.AddItems([][]byte{item})
 			}
-		}()
+		}(i)
 	}
 	for i := 0; i < itemsCount; i++ {
 		workCh <- i