diff --git a/go.mod b/go.mod
index 28bdd2ff4..7f1df8747 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,7 @@ module github.com/cayleygraph/cayley
 go 1.12
 
 require (
+	github.com/RyouZhang/async-go v0.2.2 // indirect
 	github.com/badgerodon/peg v0.0.0-20130729175151-9e5f7f4d07ca
 	github.com/cayleygraph/quad v1.2.4
 	github.com/cockroachdb/apd v1.1.0 // indirect
diff --git a/go.sum b/go.sum
index 24da5c1c9..6207bfe6b 100644
--- a/go.sum
+++ b/go.sum
@@ -12,6 +12,8 @@ github.com/Microsoft/go-winio v0.4.12/go.mod h1:VhR8bwka0BXejwEJY73c50VrPtXAaKcy
 github.com/Nvveen/Gotty v0.0.0-20120604004816-cd527374f1e5 h1:TngWCqHvy9oXAN6lEVMRuU21PR1EtLVZJmdB18Gu3Rw=
 github.com/Nvveen/Gotty v0.0.0-20120604004816-cd527374f1e5/go.mod h1:lmUJ/7eu/Q8D7ML55dXQrVaamCz2vxCfdQBasLZfHKk=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
+github.com/RyouZhang/async-go v0.2.2 h1:/cRhxuJkRLygF/a+c9Teaa96QIY22mOx1YrOK+WSgAA=
+github.com/RyouZhang/async-go v0.2.2/go.mod h1:ogL6baAxf0sZWPi/i9i4XdTt8D1Vn/AxNeG0eUWrY18=
 github.com/Shopify/sarama v1.19.0/go.mod h1:FVkBWblsNy7DGZRfXLU0O9RCGt5g3g3yEuWXgklEdEo=
 github.com/Shopify/toxiproxy v2.1.4+incompatible/go.mod h1:OXgGpZ6Cli1/URJOF1DMxUHB2q5Ap20/P/eIdh4G0pI=
 github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
diff --git a/graph/memstore/all_iterator.go b/graph/memstore/all_iterator.go
index 8a26424f8..3981ac4f7 100644
--- a/graph/memstore/all_iterator.go
+++ b/graph/memstore/all_iterator.go
@@ -178,7 +178,9 @@ func (it *allIteratorContains) Contains(ctx context.Context, v graph.Ref) bool {
 	if !ok {
 		return false
 	}
+	it.qs.primMu.RLock()
 	p := it.qs.prim[id]
+	it.qs.primMu.RUnlock()
 	if p.ID > it.maxid {
 		return false
 	}
diff --git a/graph/memstore/quadstore.go b/graph/memstore/quadstore.go
index ea9798c4d..f7a667be0 100644
--- a/graph/memstore/quadstore.go
+++ b/graph/memstore/quadstore.go
@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/cayleygraph/cayley/graph"
 	"github.com/cayleygraph/cayley/graph/iterator"
@@ -60,7 +61,7 @@ type QuadDirectionIndex struct {
 }
 
 func NewQuadDirectionIndex() QuadDirectionIndex {
-	return QuadDirectionIndex{[...]map[int64]*Tree{
+	return QuadDirectionIndex{index: [...]map[int64]*Tree{
 		quad.Subject - 1:   make(map[int64]*Tree),
 		quad.Predicate - 1: make(map[int64]*Tree),
 		quad.Object - 1:    make(map[int64]*Tree),
@@ -72,6 +73,7 @@ func (qdi QuadDirectionIndex) Tree(d quad.Direction, id int64) *Tree {
 	if d < quad.Subject || d > quad.Label {
 		panic("illegal direction")
 	}
+
 	tree, ok := qdi.index[d-1][id]
 	if !ok {
 		tree = TreeNew(cmp)
@@ -143,6 +145,11 @@ type QuadStore struct {
 	index   QuadDirectionIndex
 	horizon int64 // used only to assign ids to tx
 	// vip_index map[string]map[int64]map[string]map[int64]*b.Tree
+
+	valsMu  sync.RWMutex
+	quadsMu sync.RWMutex
+	primMu  sync.RWMutex
+	indexMu sync.RWMutex
 }
 
 // New creates a new in-memory quad store and loads provided quads.
@@ -178,7 +185,10 @@ func (qs *QuadStore) addPrimitive(p *Primitive) int64 {
 }
 
 func (qs *QuadStore) appendPrimitive(p *Primitive) {
+	qs.primMu.Lock()
 	qs.prim[p.ID] = p
+	qs.primMu.Unlock()
+
 	if !qs.reading {
 		qs.all = append(qs.all, p)
 	} else {
@@ -198,24 +208,36 @@ func (qs *QuadStore) resolveVal(v quad.Value, add bool) (int64, bool) {
 		n = n[len(internalBNodePrefix):]
 		id, err := strconv.ParseInt(string(n), 10, 64)
 		if err == nil && id != 0 {
+			qs.primMu.RLock()
 			if p, ok := qs.prim[id]; ok || !add {
+				qs.primMu.RUnlock()
 				if add {
 					p.refs++
 				}
 				return id, ok
 			}
+			qs.primMu.RUnlock()
 			qs.appendPrimitive(&Primitive{ID: id, refs: 1})
 			return id, true
 		}
 	}
 	vs := v.String()
+	qs.valsMu.RLock()
 	if id, exists := qs.vals[vs]; exists || !add {
+		qs.valsMu.RUnlock()
 		if exists && add {
+			qs.primMu.Lock()
 			qs.prim[id].refs++
+			qs.primMu.Unlock()
 		}
 		return id, exists
 	}
+	qs.valsMu.RUnlock()
+
 	id := qs.addPrimitive(&Primitive{Value: v})
+
+	qs.valsMu.Lock()
+	defer qs.valsMu.Unlock()
 	qs.vals[vs] = id
 	return id, true
 }
@@ -237,7 +259,9 @@ func (qs *QuadStore) resolveQuad(q quad.Quad, add bool) (internalQuad, bool) {
 }
 
 func (qs *QuadStore) lookupVal(id int64) quad.Value {
+	qs.primMu.RLock()
 	pv := qs.prim[id]
+	qs.primMu.RUnlock()
 	if pv == nil || pv.Value == nil {
 		return quad.BNode(internalBNodePrefix + strconv.FormatInt(id, 10))
 	}
@@ -270,6 +294,9 @@ func (qs *QuadStore) AddValue(v quad.Value) (int64, bool) {
 }
 
 func (qs *QuadStore) indexesForQuad(q internalQuad) []*Tree {
+	qs.indexMu.Lock()
+	defer qs.indexMu.Unlock()
+
 	trees := make([]*Tree, 0, 4)
 	for dir := quad.Subject; dir <= quad.Label; dir++ {
 		v := q.Dir(dir)
@@ -285,13 +312,20 @@ func (qs *QuadStore) indexesForQuad(q internalQuad) []*Tree {
 // False is returned as a second parameter if quad exists already.
 func (qs *QuadStore) AddQuad(q quad.Quad) (int64, bool) {
 	p, _ := qs.resolveQuad(q, false)
+	qs.quadsMu.RLock()
 	if id := qs.quads[p]; id != 0 {
+		qs.quadsMu.RUnlock()
 		return id, false
 	}
+	qs.quadsMu.RUnlock()
 	p, _ = qs.resolveQuad(q, true)
 	pr := &Primitive{Quad: p}
 	id := qs.addPrimitive(pr)
+
+	qs.quadsMu.Lock()
 	qs.quads[p] = id
+	qs.quadsMu.Unlock()
+
 	for _, t := range qs.indexesForQuad(p) {
 		t.Set(id, pr)
 	}
@@ -345,32 +379,44 @@ func (qs *QuadStore) deleteQuadNodes(q internalQuad) {
 		if id == 0 {
 			continue
 		}
+		qs.primMu.RLock()
 		if p := qs.prim[id]; p != nil {
+			qs.primMu.RUnlock()
 			p.refs--
 			if p.refs < 0 {
 				panic("remove of deleted node")
 			} else if p.refs == 0 {
 				qs.Delete(id)
 			}
+		} else {
+			qs.primMu.RUnlock()
 		}
 	}
 }
 func (qs *QuadStore) Delete(id int64) bool {
+	qs.primMu.RLock()
 	p := qs.prim[id]
+	qs.primMu.RUnlock()
 	if p == nil {
 		return false
 	}
 	// remove from value index
 	if p.Value != nil {
+		qs.valsMu.Lock()
 		delete(qs.vals, p.Value.String())
+		qs.valsMu.Unlock()
 	}
 	// remove from quad indexes
 	for _, t := range qs.indexesForQuad(p.Quad) {
 		t.Delete(id)
 	}
+	qs.quadsMu.Lock()
 	delete(qs.quads, p.Quad)
-	// remove primitive
+	qs.quadsMu.Unlock()
+	// remove Primitive
+	qs.primMu.Lock()
 	delete(qs.prim, id)
+	qs.primMu.Unlock()
 	di := -1
 	for i, p2 := range qs.all {
 		if p == p2 {
@@ -398,6 +444,8 @@ func (qs *QuadStore) findQuad(q quad.Quad) (int64, internalQuad, bool) {
 	if !ok {
 		return 0, p, false
 	}
+	qs.quadsMu.Lock()
+	defer qs.quadsMu.Unlock()
 	id := qs.quads[p]
 	return id, p, id != 0
 }
@@ -456,7 +504,9 @@ func asID(v graph.Ref) (int64, bool) {
 func (qs *QuadStore) quad(v graph.Ref) (q internalQuad, ok bool) {
 	switch v := v.(type) {
 	case bnode:
+		qs.primMu.RLock()
 		p := qs.prim[int64(v)]
+		qs.primMu.RUnlock()
 		if p == nil {
 			return
 		}
@@ -482,7 +532,9 @@ func (qs *QuadStore) QuadIterator(d quad.Direction, value graph.Ref) iterator.Sh
 	if !ok {
 		return iterator.NewNull()
 	}
+	qs.indexMu.RLock()
 	index, ok := qs.index.Get(d, id)
+	qs.indexMu.RUnlock()
 	if ok && index.Len() != 0 {
 		return qs.newIterator(index, d, id)
 	}
@@ -494,7 +546,9 @@ func (qs *QuadStore) QuadIteratorSize(ctx context.Context, d quad.Direction, v g
 	if !ok {
 		return refs.Size{Value: 0, Exact: true}, nil
 	}
+	qs.indexMu.RLock()
 	index, ok := qs.index.Get(d, id)
+	qs.indexMu.RUnlock()
 	if !ok {
 		return refs.Size{Value: 0, Exact: true}, nil
 	}
@@ -502,6 +556,10 @@ func (qs *QuadStore) QuadIteratorSize(ctx context.Context, d quad.Direction, v g
 }
 
 func (qs *QuadStore) Stats(ctx context.Context, exact bool) (graph.Stats, error) {
+	qs.valsMu.RLock()
+	defer qs.valsMu.RUnlock()
+	qs.quadsMu.RLock()
+	defer qs.quadsMu.RUnlock()
 	return graph.Stats{
 		Nodes: refs.Size{
 			Value: int64(len(qs.vals)),
@@ -518,7 +576,10 @@ func (qs *QuadStore) ValueOf(name quad.Value) (graph.Ref, error) {
 	if name == nil {
 		return nil, nil
 	}
+
+	qs.valsMu.Lock()
 	id := qs.vals[name.String()]
+	qs.valsMu.Unlock()
 	if id == 0 {
 		return nil, nil
 	}
@@ -535,9 +596,12 @@ func (qs *QuadStore) NameOf(v graph.Ref) (quad.Value, error) {
 	if !ok {
 		return nil, nil
 	}
+	qs.primMu.RLock()
 	if _, ok = qs.prim[n]; !ok {
+		qs.primMu.RUnlock()
 		return nil, nil
 	}
+	qs.primMu.RUnlock()
 	return qs.lookupVal(n), nil
 }
 
diff --git a/graph/memstore/quadstore_test.go b/graph/memstore/quadstore_test.go
index 0330d11a2..19edd2a54 100644
--- a/graph/memstore/quadstore_test.go
+++ b/graph/memstore/quadstore_test.go
@@ -16,9 +16,11 @@ package memstore
 
 import (
 	"context"
+	"fmt"
 	"reflect"
 	"sort"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/require"
 
@@ -26,9 +28,12 @@ import (
 	"github.com/cayleygraph/cayley/graph/graphtest"
 	"github.com/cayleygraph/cayley/graph/iterator"
 	"github.com/cayleygraph/cayley/graph/refs"
+	"github.com/cayleygraph/cayley/query/path"
 	"github.com/cayleygraph/cayley/query/shape"
 	"github.com/cayleygraph/cayley/writer"
 	"github.com/cayleygraph/quad"
+
+	"github.com/RyouZhang/async-go"
 )
 
 // This is a simple test graph.
@@ -264,3 +269,42 @@ func TestTransaction(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, st, st2, "Appended a new quad in a failed transaction")
 }
+
+// test multi thread insert and query
+func TestMultiThreadQuery(t *testing.T) {
+	qs, _, _ := makeTestStore(simpleGraph)
+
+	// we make 50 insert, 50 query
+	funcs := make([]async.LambdaMethod, 100)
+	for i := 0; i < 100; i++ {
+		if i%2 == 0 {
+			index := i
+			funcs[i] = func() (interface{}, error) {
+				id, flag := qs.AddQuad(quad.Make(
+					fmt.Sprintf("E_%d", index), "follows", "G", nil),
+				)
+				if !flag {
+					return nil, fmt.Errorf("quard exist:%d", id)
+				}
+				return id, nil
+			}
+		} else {
+			funcs[i] = func() (interface{}, error) {
+				ctx := context.Background()
+				followers, err := path.StartPath(qs, quad.Raw("G")).In("follows").Iterate(ctx).AllValues(qs)
+				if err != nil {
+					return nil, err
+				}
+				return followers, nil
+			}
+		}
+	}
+
+	results := async.All(funcs, 1*time.Second)
+	for _, result := range results {
+		switch result.(type) {
+		case error:
+			require.NoError(t, result.(error))
+		}
+	}
+}
diff --git a/graph/nosql/elastic/elastic.go b/graph/nosql/elastic/elastic.go
index 840d5f0b3..2cb7883c1 100644
--- a/graph/nosql/elastic/elastic.go
+++ b/graph/nosql/elastic/elastic.go
@@ -6,7 +6,6 @@ import (
 	"github.com/hidal-go/hidalgo/legacy/nosql/elastic"
 	//import hidal-go first so the registration of the no sql stores occurs before quadstore iterates for registration
 	gnosql "github.com/cayleygraph/cayley/graph/nosql"
-	
 )
 
 const Type = elastic.Name
diff --git a/graph/nosql/mongo/mongo.go b/graph/nosql/mongo/mongo.go
index 0b2649b0c..2dcdc1388 100644
--- a/graph/nosql/mongo/mongo.go
+++ b/graph/nosql/mongo/mongo.go
@@ -6,7 +6,6 @@ import (
 	"github.com/hidal-go/hidalgo/legacy/nosql/mongo"
 	//import hidal-go first so the registration of the no sql stores occurs before quadstore iterates for registration
 	gnosql "github.com/cayleygraph/cayley/graph/nosql"
-	
 )
 
 const Type = mongo.Name