diff --git a/cmd/routedns/main.go b/cmd/routedns/main.go
index 18699f34..f50ae20e 100644
--- a/cmd/routedns/main.go
+++ b/cmd/routedns/main.go
@@ -272,6 +272,11 @@ func instantiateGroup(id string, g group, resolvers map[string]rdns.Resolver) er
 		gr = append(gr, resolver)
 	}
 	switch g.Type {
+    case "lock-duplicate-request":
+		if len(gr) != 1 {
+			return fmt.Errorf("type lock-duplicate-request only supports one resolver in '%s'", id)
+		}
+		resolvers[id] = rdns.NewlockDuplicateRequest(id, gr[0])
 	case "round-robin":
 		resolvers[id] = rdns.NewRoundRobin(id, gr...)
 	case "fail-rotate":
diff --git a/lockduplicaterequest.go b/lockduplicaterequest.go
new file mode 100644
index 00000000..ffcebeda
--- /dev/null
+++ b/lockduplicaterequest.go
@@ -0,0 +1,174 @@
+package rdns
+
+import (
+	"encoding/binary"
+	"github.com/miekg/dns"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+type key struct {
+	name        string
+	qtype       uint16
+	ecs_ipv4    uint32
+	ecs_ipv6_hi uint64
+	ecs_ipv6_lo uint64
+	ecs_mask    uint8
+}
+
+type value struct {
+	//If expiredTimeStamp is negative number , it means it will return SERVFAIL.
+	expiredTimeStamp int64
+	mu               *newMutex
+}
+
+type lockDuplicateRequest struct {
+	id       string
+	resolver Resolver
+	m        sync.Map
+}
+
+var _ Resolver = &lockDuplicateRequest{}
+
+func NewlockDuplicateRequest(id string, resolver Resolver) *lockDuplicateRequest {
+	ret := &lockDuplicateRequest{id: id, resolver: resolver}
+	return ret
+}
+
+func (r *lockDuplicateRequest) Resolve(q *dns.Msg, ci ClientInfo) (*dns.Msg, error) {
+
+	var ecsipv4 uint32 = 0
+	var ecsipv6hi uint64 = 0
+	var ecsipv6lo uint64 = 0
+	var ecsmask uint8 = 0
+
+	if len(q.Question) != 1 {
+		return r.resolver.Resolve(q, ci)
+	}
+
+	edns0 := q.IsEdns0()
+	if edns0 != nil {
+		// Find the ECS option
+		for _, opt := range edns0.Option {
+			ecs, ok := opt.(*dns.EDNS0_SUBNET)
+			if !ok {
+				continue
+			}
+			switch ecs.Family {
+			case 1: // ip4
+				ecsipv4 = ldrByteToUint32(ecs.Address.To4())
+				ecsmask = ecs.SourceNetmask
+				break
+			case 2: // ip6
+				ecsipv6hi, ecsipv6lo = ldrByteToUint128(ecs.Address.To16())
+				ecsmask = ecs.SourceNetmask
+				break
+			}
+		}
+	}
+
+	k := key{
+		name:        q.Question[0].Name,
+		qtype:       q.Question[0].Qtype,
+		ecs_ipv4:    ecsipv4,
+		ecs_ipv6_hi: ecsipv6hi,
+		ecs_ipv6_lo: ecsipv6lo,
+		ecs_mask:    ecsmask,
+	}
+
+	var newValue value
+	parse, _ := time.ParseDuration("+5s")
+	expired := time.Now().Add(parse)
+	newValue.expiredTimeStamp = expired.Unix()
+	newValue.mu = &newMutex{}
+	loaded, _ := r.m.LoadOrStore(k, newValue)
+	v := loaded.(value)
+
+
+	var returnAnswer *dns.Msg
+	var returnError error
+
+	v.mu.Lock()
+	if v.expiredTimeStamp >= 0 {
+		a, err := r.resolver.Resolve(q, ci)
+		returnAnswer = a
+		returnError = err
+	} else {
+		returnAnswer = nil
+		returnError = QueryTimeoutError{q}
+	}
+	v.mu.UnLock()
+
+	currentTimeStamp := time.Now().Unix()
+	expiredTimeStamp := v.expiredTimeStamp
+	if v.mu.Count() == 0 {
+		r.m.Delete(k)
+	} else if expiredTimeStamp >= 0 && expiredTimeStamp < currentTimeStamp {
+		r.m.Delete(k)
+		v.expiredTimeStamp = ^expiredTimeStamp
+		v.mu.UnLockAll()
+	}
+
+	return returnAnswer, returnError
+}
+
+func (r *lockDuplicateRequest) String() string {
+	return r.id
+}
+
+func ldrByteToUint128(b []byte) (uint64, uint64) {
+	hi := binary.BigEndian.Uint64(b[0:8])
+	lo := binary.BigEndian.Uint64(b[8:16])
+	return hi, lo
+}
+
+func ldrByteToUint32(b []byte) uint32 {
+	return binary.BigEndian.Uint32(b[0:4])
+}
+
+type newMutex struct {
+	count uint32
+	sync  sync.Mutex
+}
+
+func (r *newMutex) Count() uint32 {
+	return r.count
+}
+
+func (r *newMutex) Lock() {
+	r.sync.Lock()
+	atomic.AddUint32(&(r.count), +1)
+}
+
+func (r *newMutex) UnLock() {
+	for {
+		count := atomic.LoadUint32(&(r.count))
+		if count > 0 {
+			ok := atomic.CompareAndSwapUint32(&(r.count), count, count-1)
+			if ok {
+				break
+			}
+		} else {
+			return
+		}
+	}
+	r.sync.Unlock()
+}
+
+func (r *newMutex) UnLockAll() {
+	for {
+		count := atomic.LoadUint32(&(r.count))
+		if count > 0 {
+			ok := atomic.CompareAndSwapUint32(&(r.count), count, 0)
+			if ok {
+				for count > 0 {
+					count--
+					r.sync.Unlock()
+				}
+			}
+		} else {
+			break
+		}
+	}
+}