diff --git a/etcdserver/api/v2v3/cluster.go b/etcdserver/api/v2v3/cluster.go
new file mode 100644
index 000000000..b53e6d7c8
--- /dev/null
+++ b/etcdserver/api/v2v3/cluster.go
@@ -0,0 +1,31 @@
+// Copyright 2017 The etcd 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 v2v3
+
+import (
+	"github.com/coreos/etcd/etcdserver/membership"
+	"github.com/coreos/etcd/pkg/types"
+
+	"github.com/coreos/go-semver/semver"
+)
+
+func (s *v2v3Server) ID() types.ID {
+	// TODO: use an actual member ID
+	return types.ID(0xe7cd2f00d)
+}
+func (s *v2v3Server) ClientURLs() []string                  { panic("STUB") }
+func (s *v2v3Server) Members() []*membership.Member         { panic("STUB") }
+func (s *v2v3Server) Member(id types.ID) *membership.Member { panic("STUB") }
+func (s *v2v3Server) Version() *semver.Version              { panic("STUB") }
diff --git a/etcdserver/api/v2v3/doc.go b/etcdserver/api/v2v3/doc.go
new file mode 100644
index 000000000..2ff372f18
--- /dev/null
+++ b/etcdserver/api/v2v3/doc.go
@@ -0,0 +1,16 @@
+// Copyright 2017 The etcd 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 v2v3 provides a ServerV2 implementation backed by clientv3.Client.
+package v2v3
diff --git a/etcdserver/api/v2v3/server.go b/etcdserver/api/v2v3/server.go
new file mode 100644
index 000000000..dae457ccf
--- /dev/null
+++ b/etcdserver/api/v2v3/server.go
@@ -0,0 +1,117 @@
+// Copyright 2017 The etcd 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 v2v3
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/coreos/etcd/clientv3"
+	"github.com/coreos/etcd/etcdserver"
+	"github.com/coreos/etcd/etcdserver/api"
+	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
+	"github.com/coreos/etcd/etcdserver/membership"
+	"github.com/coreos/etcd/pkg/types"
+
+	"github.com/coreos/go-semver/semver"
+	"golang.org/x/net/context" // TODO: replace with context in go1.9
+)
+
+type fakeStats struct{}
+
+func (s *fakeStats) SelfStats() []byte   { return nil }
+func (s *fakeStats) LeaderStats() []byte { return nil }
+func (s *fakeStats) StoreStats() []byte  { return nil }
+
+type v2v3Server struct {
+	c     *clientv3.Client
+	store *v2v3Store
+	fakeStats
+}
+
+func NewServer(c *clientv3.Client, pfx string) etcdserver.ServerPeer {
+	return &v2v3Server{c: c, store: newStore(c, pfx)}
+}
+
+func (s *v2v3Server) ClientCertAuthEnabled() bool { return false }
+
+func (s *v2v3Server) LeaseHandler() http.Handler { panic("STUB: lease handler") }
+func (s *v2v3Server) RaftHandler() http.Handler  { panic("STUB: raft handler") }
+
+func (s *v2v3Server) Leader() types.ID {
+	ctx, cancel := context.WithTimeout(context.TODO(), 5*time.Second)
+	defer cancel()
+	resp, err := s.c.Status(ctx, s.c.Endpoints()[0])
+	if err != nil {
+		return 0
+	}
+	return types.ID(resp.Leader)
+}
+
+func (s *v2v3Server) AddMember(ctx context.Context, memb membership.Member) ([]*membership.Member, error) {
+	resp, err := s.c.MemberAdd(ctx, memb.PeerURLs)
+	if err != nil {
+		return nil, err
+	}
+	return v3MembersToMembership(resp.Members), nil
+}
+
+func (s *v2v3Server) RemoveMember(ctx context.Context, id uint64) ([]*membership.Member, error) {
+	resp, err := s.c.MemberRemove(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	return v3MembersToMembership(resp.Members), nil
+}
+
+func (s *v2v3Server) UpdateMember(ctx context.Context, m membership.Member) ([]*membership.Member, error) {
+	resp, err := s.c.MemberUpdate(ctx, uint64(m.ID), m.PeerURLs)
+	if err != nil {
+		return nil, err
+	}
+	return v3MembersToMembership(resp.Members), nil
+}
+
+func v3MembersToMembership(v3membs []*pb.Member) []*membership.Member {
+	membs := make([]*membership.Member, len(v3membs))
+	for i, m := range v3membs {
+		membs[i] = &membership.Member{
+			ID: types.ID(m.ID),
+			RaftAttributes: membership.RaftAttributes{
+				PeerURLs: m.PeerURLs,
+			},
+			Attributes: membership.Attributes{
+				Name:       m.Name,
+				ClientURLs: m.ClientURLs,
+			},
+		}
+	}
+	return membs
+}
+
+func (s *v2v3Server) ClusterVersion() *semver.Version { return s.Version() }
+func (s *v2v3Server) Cluster() api.Cluster            { return s }
+func (s *v2v3Server) Alarms() []*pb.AlarmMember       { return nil }
+
+func (s *v2v3Server) Do(ctx context.Context, r pb.Request) (etcdserver.Response, error) {
+	applier := etcdserver.NewApplierV2(s.store, nil)
+	reqHandler := etcdserver.NewStoreRequestV2Handler(s.store, applier)
+	req := (*etcdserver.RequestV2)(&r)
+	resp, err := req.Handle(ctx, reqHandler)
+	if resp.Err != nil {
+		return resp, resp.Err
+	}
+	return resp, err
+}
diff --git a/etcdserver/api/v2v3/store.go b/etcdserver/api/v2v3/store.go
new file mode 100644
index 000000000..22227f8aa
--- /dev/null
+++ b/etcdserver/api/v2v3/store.go
@@ -0,0 +1,621 @@
+// Copyright 2017 The etcd 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 v2v3
+
+import (
+	"context"
+	"fmt"
+	"path"
+	"strings"
+	"time"
+
+	"github.com/coreos/etcd/clientv3"
+	"github.com/coreos/etcd/clientv3/concurrency"
+	etcdErr "github.com/coreos/etcd/error"
+	"github.com/coreos/etcd/mvcc/mvccpb"
+	"github.com/coreos/etcd/store"
+)
+
+// store implements the Store interface for V2 using
+// a v3 client.
+type v2v3Store struct {
+	c *clientv3.Client
+	// pfx is the v3 prefix where keys should be stored.
+	pfx string
+	ctx context.Context
+}
+
+const maxPathDepth = 63
+
+var errUnsupported = fmt.Errorf("TTLs are unsupported")
+
+func NewStore(c *clientv3.Client, pfx string) store.Store { return newStore(c, pfx) }
+
+func newStore(c *clientv3.Client, pfx string) *v2v3Store { return &v2v3Store{c, pfx, c.Ctx()} }
+
+func (s *v2v3Store) Index() uint64 { panic("STUB") }
+
+func (s *v2v3Store) Get(nodePath string, recursive, sorted bool) (*store.Event, error) {
+	key := s.mkPath(nodePath)
+	resp, err := s.c.Txn(s.ctx).Then(
+		clientv3.OpGet(key+"/"),
+		clientv3.OpGet(key),
+	).Commit()
+	if err != nil {
+		return nil, err
+	}
+
+	if kvs := resp.Responses[0].GetResponseRange().Kvs; len(kvs) != 0 || isRoot(nodePath) {
+		nodes, err := s.getDir(nodePath, recursive, sorted, resp.Header.Revision)
+		if err != nil {
+			return nil, err
+		}
+		cidx, midx := uint64(0), uint64(0)
+		if len(kvs) > 0 {
+			cidx, midx = mkV2Rev(kvs[0].CreateRevision), mkV2Rev(kvs[0].ModRevision)
+		}
+		return &store.Event{
+			Action: store.Get,
+			Node: &store.NodeExtern{
+				Key:           nodePath,
+				Dir:           true,
+				Nodes:         nodes,
+				CreatedIndex:  cidx,
+				ModifiedIndex: midx,
+			},
+			EtcdIndex: mkV2Rev(resp.Header.Revision),
+		}, nil
+	}
+
+	kvs := resp.Responses[1].GetResponseRange().Kvs
+	if len(kvs) == 0 {
+		return nil, etcdErr.NewError(etcdErr.EcodeKeyNotFound, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+
+	return &store.Event{
+		Action:    store.Get,
+		Node:      s.mkV2Node(kvs[0]),
+		EtcdIndex: mkV2Rev(resp.Header.Revision),
+	}, nil
+}
+
+func (s *v2v3Store) getDir(nodePath string, recursive, sorted bool, rev int64) ([]*store.NodeExtern, error) {
+	rootNodes, err := s.getDirDepth(nodePath, 1, rev)
+	if err != nil || !recursive {
+		return rootNodes, err
+	}
+	nextNodes := rootNodes
+	nodes := make(map[string]*store.NodeExtern)
+	// Breadth walk the subdirectories
+	for i := 2; len(nextNodes) > 0; i++ {
+		for _, n := range nextNodes {
+			nodes[n.Key] = n
+			if parent := nodes[path.Dir(n.Key)]; parent != nil {
+				parent.Nodes = append(parent.Nodes, n)
+			}
+		}
+		if nextNodes, err = s.getDirDepth(nodePath, i, rev); err != nil {
+			return nil, err
+		}
+	}
+	return rootNodes, nil
+}
+
+func (s *v2v3Store) getDirDepth(nodePath string, depth int, rev int64) ([]*store.NodeExtern, error) {
+	pd := s.mkPathDepth(nodePath, depth)
+	resp, err := s.c.Get(s.ctx, pd, clientv3.WithPrefix(), clientv3.WithRev(rev))
+	if err != nil {
+		return nil, err
+	}
+
+	nodes := make([]*store.NodeExtern, len(resp.Kvs))
+	for i, kv := range resp.Kvs {
+		nodes[i] = s.mkV2Node(kv)
+	}
+	return nodes, nil
+}
+
+func (s *v2v3Store) Set(
+	nodePath string,
+	dir bool,
+	value string,
+	expireOpts store.TTLOptionSet,
+) (*store.Event, error) {
+	if expireOpts.Refresh || !expireOpts.ExpireTime.IsZero() {
+		return nil, errUnsupported
+	}
+
+	if isRoot(nodePath) {
+		return nil, etcdErr.NewError(etcdErr.EcodeRootROnly, nodePath, 0)
+	}
+
+	ecode := 0
+	applyf := func(stm concurrency.STM) error {
+		parent := path.Dir(nodePath)
+		if !isRoot(parent) && stm.Rev(s.mkPath(parent)+"/") == 0 {
+			ecode = etcdErr.EcodeKeyNotFound
+			return nil
+		}
+
+		key := s.mkPath(nodePath)
+		if dir {
+			if stm.Rev(key) != 0 {
+				// exists as non-dir
+				ecode = etcdErr.EcodeNotDir
+				return nil
+			}
+			key = key + "/"
+		} else if stm.Rev(key+"/") != 0 {
+			ecode = etcdErr.EcodeNotFile
+			return nil
+		}
+		stm.Put(key, value, clientv3.WithPrevKV())
+		stm.Put(s.mkActionKey(), store.Set)
+		return nil
+	}
+
+	resp, err := s.newSTM(applyf)
+	if err != nil {
+		return nil, err
+	}
+	if ecode != 0 {
+		return nil, etcdErr.NewError(ecode, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+
+	createRev := resp.Header.Revision
+	var pn *store.NodeExtern
+	if pkv := prevKeyFromPuts(resp); pkv != nil {
+		pn = s.mkV2Node(pkv)
+		createRev = pkv.CreateRevision
+	}
+
+	vp := &value
+	if dir {
+		vp = nil
+	}
+	return &store.Event{
+		Action: store.Set,
+		Node: &store.NodeExtern{
+			Key:           nodePath,
+			Value:         vp,
+			Dir:           dir,
+			ModifiedIndex: mkV2Rev(resp.Header.Revision),
+			CreatedIndex:  mkV2Rev(createRev),
+		},
+		PrevNode:  pn,
+		EtcdIndex: mkV2Rev(resp.Header.Revision),
+	}, nil
+}
+
+func (s *v2v3Store) Update(nodePath, newValue string, expireOpts store.TTLOptionSet) (*store.Event, error) {
+	if isRoot(nodePath) {
+		return nil, etcdErr.NewError(etcdErr.EcodeRootROnly, nodePath, 0)
+	}
+
+	if expireOpts.Refresh || !expireOpts.ExpireTime.IsZero() {
+		return nil, errUnsupported
+	}
+
+	key := s.mkPath(nodePath)
+	ecode := 0
+	applyf := func(stm concurrency.STM) error {
+		if rev := stm.Rev(key + "/"); rev != 0 {
+			ecode = etcdErr.EcodeNotFile
+			return nil
+		}
+		if rev := stm.Rev(key); rev == 0 {
+			ecode = etcdErr.EcodeKeyNotFound
+			return nil
+		}
+		stm.Put(key, newValue, clientv3.WithPrevKV())
+		stm.Put(s.mkActionKey(), store.Update)
+		return nil
+	}
+
+	resp, err := s.newSTM(applyf)
+	if err != nil {
+		return nil, err
+	}
+	if ecode != 0 {
+		return nil, etcdErr.NewError(etcdErr.EcodeNotFile, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+
+	pkv := prevKeyFromPuts(resp)
+	return &store.Event{
+		Action: store.Update,
+		Node: &store.NodeExtern{
+			Key:           nodePath,
+			Value:         &newValue,
+			ModifiedIndex: mkV2Rev(resp.Header.Revision),
+			CreatedIndex:  mkV2Rev(pkv.CreateRevision),
+		},
+		PrevNode:  s.mkV2Node(pkv),
+		EtcdIndex: mkV2Rev(resp.Header.Revision),
+	}, nil
+}
+
+func (s *v2v3Store) Create(
+	nodePath string,
+	dir bool,
+	value string,
+	unique bool,
+	expireOpts store.TTLOptionSet,
+) (*store.Event, error) {
+	if isRoot(nodePath) {
+		return nil, etcdErr.NewError(etcdErr.EcodeRootROnly, nodePath, 0)
+	}
+	if expireOpts.Refresh || !expireOpts.ExpireTime.IsZero() {
+		return nil, errUnsupported
+	}
+	ecode := 0
+	applyf := func(stm concurrency.STM) error {
+		ecode = 0
+		key := s.mkPath(nodePath)
+		if unique {
+			// append unique item under the node path
+			for {
+				key = nodePath + "/" + fmt.Sprintf("%020s", time.Now())
+				key = path.Clean(path.Join("/", key))
+				key = s.mkPath(key)
+				if stm.Rev(key) == 0 {
+					break
+				}
+			}
+		}
+		if stm.Rev(key) > 0 || stm.Rev(key+"/") > 0 {
+			ecode = etcdErr.EcodeNodeExist
+			return nil
+		}
+		// build path if any directories in path do not exist
+		dirs := []string{}
+		for p := path.Dir(nodePath); !isRoot(p); p = path.Dir(p) {
+			pp := s.mkPath(p)
+			if stm.Rev(pp) > 0 {
+				ecode = etcdErr.EcodeNotDir
+				return nil
+			}
+			if stm.Rev(pp+"/") == 0 {
+				dirs = append(dirs, pp+"/")
+			}
+		}
+		for _, d := range dirs {
+			stm.Put(d, "")
+		}
+
+		if dir {
+			// directories marked with extra slash in key name
+			key += "/"
+		}
+		stm.Put(key, value)
+		stm.Put(s.mkActionKey(), store.Create)
+		return nil
+	}
+
+	resp, err := s.newSTM(applyf)
+	if err != nil {
+		return nil, err
+	}
+	if ecode != 0 {
+		return nil, etcdErr.NewError(ecode, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+
+	var v *string
+	if !dir {
+		v = &value
+	}
+
+	return &store.Event{
+		Action: store.Create,
+		Node: &store.NodeExtern{
+			Key:           nodePath,
+			Value:         v,
+			Dir:           dir,
+			ModifiedIndex: mkV2Rev(resp.Header.Revision),
+			CreatedIndex:  mkV2Rev(resp.Header.Revision),
+		},
+		EtcdIndex: mkV2Rev(resp.Header.Revision),
+	}, nil
+}
+
+func (s *v2v3Store) CompareAndSwap(
+	nodePath string,
+	prevValue string,
+	prevIndex uint64,
+	value string,
+	expireOpts store.TTLOptionSet,
+) (*store.Event, error) {
+	if isRoot(nodePath) {
+		return nil, etcdErr.NewError(etcdErr.EcodeRootROnly, nodePath, 0)
+	}
+	if expireOpts.Refresh || !expireOpts.ExpireTime.IsZero() {
+		return nil, errUnsupported
+	}
+
+	key := s.mkPath(nodePath)
+	resp, err := s.c.Txn(s.ctx).If(
+		s.mkCompare(nodePath, prevValue, prevIndex)...,
+	).Then(
+		clientv3.OpPut(key, value, clientv3.WithPrevKV()),
+		clientv3.OpPut(s.mkActionKey(), store.CompareAndSwap),
+	).Else(
+		clientv3.OpGet(key),
+		clientv3.OpGet(key+"/"),
+	).Commit()
+
+	if err != nil {
+		return nil, err
+	}
+	if !resp.Succeeded {
+		return nil, compareFail(nodePath, prevValue, prevIndex, resp)
+	}
+
+	pkv := resp.Responses[0].GetResponsePut().PrevKv
+	return &store.Event{
+		Action: store.CompareAndSwap,
+		Node: &store.NodeExtern{
+			Key:           nodePath,
+			Value:         &value,
+			CreatedIndex:  mkV2Rev(pkv.CreateRevision),
+			ModifiedIndex: mkV2Rev(resp.Header.Revision),
+		},
+		PrevNode:  s.mkV2Node(pkv),
+		EtcdIndex: mkV2Rev(resp.Header.Revision),
+	}, nil
+}
+
+func (s *v2v3Store) Delete(nodePath string, dir, recursive bool) (*store.Event, error) {
+	if isRoot(nodePath) {
+		return nil, etcdErr.NewError(etcdErr.EcodeRootROnly, nodePath, 0)
+	}
+	if !dir && !recursive {
+		return s.deleteNode(nodePath)
+	}
+	dir = true
+	if !recursive {
+		return s.deleteEmptyDir(nodePath)
+	}
+
+	dels := make([]clientv3.Op, maxPathDepth+1)
+	dels[0] = clientv3.OpDelete(s.mkPath(nodePath)+"/", clientv3.WithPrevKV())
+	for i := 1; i < maxPathDepth; i++ {
+		dels[i] = clientv3.OpDelete(s.mkPathDepth(nodePath, i), clientv3.WithPrefix())
+	}
+	dels[maxPathDepth] = clientv3.OpPut(s.mkActionKey(), store.Delete)
+
+	resp, err := s.c.Txn(s.ctx).If(
+		clientv3.Compare(clientv3.Version(s.mkPath(nodePath)+"/"), ">", 0),
+		clientv3.Compare(clientv3.Version(s.mkPathDepth(nodePath, maxPathDepth)+"/"), "=", 0),
+	).Then(
+		dels...,
+	).Commit()
+	if err != nil {
+		return nil, err
+	}
+	if !resp.Succeeded {
+		return nil, etcdErr.NewError(etcdErr.EcodeNodeExist, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+	dresp := resp.Responses[0].GetResponseDeleteRange()
+	return &store.Event{
+		Action:    store.Delete,
+		PrevNode:  s.mkV2Node(dresp.PrevKvs[0]),
+		EtcdIndex: mkV2Rev(resp.Header.Revision),
+	}, nil
+}
+
+func (s *v2v3Store) deleteEmptyDir(nodePath string) (*store.Event, error) {
+	resp, err := s.c.Txn(s.ctx).If(
+		clientv3.Compare(clientv3.Version(s.mkPathDepth(nodePath, 1)), "=", 0).WithPrefix(),
+	).Then(
+		clientv3.OpDelete(s.mkPath(nodePath)+"/", clientv3.WithPrevKV()),
+		clientv3.OpPut(s.mkActionKey(), store.Delete),
+	).Commit()
+	if err != nil {
+		return nil, err
+	}
+	if !resp.Succeeded {
+		return nil, etcdErr.NewError(etcdErr.EcodeDirNotEmpty, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+	dresp := resp.Responses[0].GetResponseDeleteRange()
+	if len(dresp.PrevKvs) == 0 {
+		return nil, etcdErr.NewError(etcdErr.EcodeNodeExist, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+	return &store.Event{
+		Action:    store.Delete,
+		PrevNode:  s.mkV2Node(dresp.PrevKvs[0]),
+		EtcdIndex: mkV2Rev(resp.Header.Revision),
+	}, nil
+}
+
+func (s *v2v3Store) deleteNode(nodePath string) (*store.Event, error) {
+	resp, err := s.c.Txn(s.ctx).If(
+		clientv3.Compare(clientv3.Version(s.mkPath(nodePath)+"/"), "=", 0),
+	).Then(
+		clientv3.OpDelete(s.mkPath(nodePath), clientv3.WithPrevKV()),
+		clientv3.OpPut(s.mkActionKey(), store.Delete),
+	).Commit()
+	if err != nil {
+		return nil, err
+	}
+	if !resp.Succeeded {
+		return nil, etcdErr.NewError(etcdErr.EcodeNotFile, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+	pkvs := resp.Responses[0].GetResponseDeleteRange().PrevKvs
+	if len(pkvs) == 0 {
+		return nil, etcdErr.NewError(etcdErr.EcodeKeyNotFound, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+	pkv := pkvs[0]
+	return &store.Event{
+		Action: store.Delete,
+		Node: &store.NodeExtern{
+			Key:           nodePath,
+			CreatedIndex:  mkV2Rev(pkv.CreateRevision),
+			ModifiedIndex: mkV2Rev(resp.Header.Revision),
+		},
+		PrevNode:  s.mkV2Node(pkv),
+		EtcdIndex: mkV2Rev(resp.Header.Revision),
+	}, nil
+}
+
+func (s *v2v3Store) CompareAndDelete(nodePath, prevValue string, prevIndex uint64) (*store.Event, error) {
+	if isRoot(nodePath) {
+		return nil, etcdErr.NewError(etcdErr.EcodeRootROnly, nodePath, 0)
+	}
+
+	key := s.mkPath(nodePath)
+	resp, err := s.c.Txn(s.ctx).If(
+		s.mkCompare(nodePath, prevValue, prevIndex)...,
+	).Then(
+		clientv3.OpDelete(key, clientv3.WithPrevKV()),
+		clientv3.OpPut(s.mkActionKey(), store.CompareAndDelete),
+	).Else(
+		clientv3.OpGet(key),
+		clientv3.OpGet(key+"/"),
+	).Commit()
+
+	if err != nil {
+		return nil, err
+	}
+	if !resp.Succeeded {
+		return nil, compareFail(nodePath, prevValue, prevIndex, resp)
+	}
+
+	// len(pkvs) > 1 since txn only succeeds when key exists
+	pkv := resp.Responses[0].GetResponseDeleteRange().PrevKvs[0]
+	return &store.Event{
+		Action: store.CompareAndDelete,
+		Node: &store.NodeExtern{
+			Key:           nodePath,
+			CreatedIndex:  mkV2Rev(pkv.CreateRevision),
+			ModifiedIndex: mkV2Rev(resp.Header.Revision),
+		},
+		PrevNode:  s.mkV2Node(pkv),
+		EtcdIndex: mkV2Rev(resp.Header.Revision),
+	}, nil
+}
+
+func compareFail(nodePath, prevValue string, prevIndex uint64, resp *clientv3.TxnResponse) error {
+	if dkvs := resp.Responses[1].GetResponseRange().Kvs; len(dkvs) > 0 {
+		return etcdErr.NewError(etcdErr.EcodeNotFile, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+	kvs := resp.Responses[0].GetResponseRange().Kvs
+	if len(kvs) == 0 {
+		return etcdErr.NewError(etcdErr.EcodeKeyNotFound, nodePath, mkV2Rev(resp.Header.Revision))
+	}
+	kv := kvs[0]
+	indexMatch := (prevIndex == 0 || kv.ModRevision == int64(prevIndex))
+	valueMatch := (prevValue == "" || string(kv.Value) == prevValue)
+	cause := ""
+	switch {
+	case indexMatch && !valueMatch:
+		cause = fmt.Sprintf("[%v != %v]", prevValue, string(kv.Value))
+	case valueMatch && !indexMatch:
+		cause = fmt.Sprintf("[%v != %v]", prevIndex, kv.ModRevision)
+	default:
+		cause = fmt.Sprintf("[%v != %v] [%v != %v]", prevValue, string(kv.Value), prevIndex, kv.ModRevision)
+	}
+	return etcdErr.NewError(etcdErr.EcodeTestFailed, cause, mkV2Rev(resp.Header.Revision))
+}
+
+func (s *v2v3Store) mkCompare(nodePath, prevValue string, prevIndex uint64) []clientv3.Cmp {
+	key := s.mkPath(nodePath)
+	cmps := []clientv3.Cmp{clientv3.Compare(clientv3.Version(key), ">", 0)}
+	if prevIndex != 0 {
+		cmps = append(cmps, clientv3.Compare(clientv3.ModRevision(key), "=", mkV3Rev(prevIndex)))
+	}
+	if prevValue != "" {
+		cmps = append(cmps, clientv3.Compare(clientv3.Value(key), "=", prevValue))
+	}
+	return cmps
+}
+
+func (s *v2v3Store) JsonStats() []byte                  { panic("STUB") }
+func (s *v2v3Store) DeleteExpiredKeys(cutoff time.Time) { panic("STUB") }
+
+func (s *v2v3Store) Version() int { return 2 }
+
+// TODO: move this out of the Store interface?
+
+func (s *v2v3Store) Save() ([]byte, error)       { panic("STUB") }
+func (s *v2v3Store) Recovery(state []byte) error { panic("STUB") }
+func (s *v2v3Store) Clone() store.Store          { panic("STUB") }
+func (s *v2v3Store) SaveNoCopy() ([]byte, error) { panic("STUB") }
+func (s *v2v3Store) HasTTLKeys() bool            { panic("STUB") }
+
+func (s *v2v3Store) mkPath(nodePath string) string { return s.mkPathDepth(nodePath, 0) }
+
+func (s *v2v3Store) mkNodePath(p string) string {
+	return path.Clean(p[len(s.pfx)+len("/k/000/"):])
+}
+
+// mkPathDepth makes a path to a key that encodes its directory depth
+// for fast directory listing. If a depth is provided, it is added
+// to the computed depth.
+func (s *v2v3Store) mkPathDepth(nodePath string, depth int) string {
+	normalForm := path.Clean(path.Join("/", nodePath))
+	n := strings.Count(normalForm, "/") + depth
+	return fmt.Sprintf("%s/%03d/k/%s", s.pfx, n, normalForm)
+}
+
+func (s *v2v3Store) mkActionKey() string { return s.pfx + "/act" }
+
+func isRoot(s string) bool { return len(s) == 0 || s == "/" || s == "/0" || s == "/1" }
+
+func mkV2Rev(v3Rev int64) uint64 {
+	if v3Rev == 0 {
+		return 0
+	}
+	return uint64(v3Rev - 1)
+}
+
+func mkV3Rev(v2Rev uint64) int64 {
+	if v2Rev == 0 {
+		return 0
+	}
+	return int64(v2Rev + 1)
+}
+
+// mkV2Node creates a V2 NodeExtern from a V3 KeyValue
+func (s *v2v3Store) mkV2Node(kv *mvccpb.KeyValue) *store.NodeExtern {
+	if kv == nil {
+		return nil
+	}
+	n := &store.NodeExtern{
+		Key:           string(s.mkNodePath(string(kv.Key))),
+		Dir:           kv.Key[len(kv.Key)-1] == '/',
+		CreatedIndex:  mkV2Rev(kv.CreateRevision),
+		ModifiedIndex: mkV2Rev(kv.ModRevision),
+	}
+	if !n.Dir {
+		v := string(kv.Value)
+		n.Value = &v
+	}
+	return n
+}
+
+// prevKeyFromPuts gets the prev key that is being put; ignores
+// the put action response.
+func prevKeyFromPuts(resp *clientv3.TxnResponse) *mvccpb.KeyValue {
+	for _, r := range resp.Responses {
+		pkv := r.GetResponsePut().PrevKv
+		if pkv != nil && pkv.CreateRevision > 0 {
+			return pkv
+		}
+	}
+	return nil
+}
+
+func (s *v2v3Store) newSTM(applyf func(concurrency.STM) error) (*clientv3.TxnResponse, error) {
+	return concurrency.NewSTM(s.c, applyf, concurrency.WithIsolation(concurrency.Serializable))
+}
diff --git a/etcdserver/api/v2v3/watcher.go b/etcdserver/api/v2v3/watcher.go
new file mode 100644
index 000000000..1c2680e74
--- /dev/null
+++ b/etcdserver/api/v2v3/watcher.go
@@ -0,0 +1,140 @@
+// Copyright 2017 The etcd 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 v2v3
+
+import (
+	"context"
+	"strings"
+
+	"github.com/coreos/etcd/clientv3"
+	etcdErr "github.com/coreos/etcd/error"
+	"github.com/coreos/etcd/store"
+)
+
+func (s *v2v3Store) Watch(prefix string, recursive, stream bool, sinceIndex uint64) (store.Watcher, error) {
+	ctx, cancel := context.WithCancel(s.ctx)
+	wch := s.c.Watch(
+		ctx,
+		// TODO: very pricey; use a single store-wide watch in future
+		s.pfx,
+		clientv3.WithPrefix(),
+		clientv3.WithRev(int64(sinceIndex)),
+		clientv3.WithCreatedNotify(),
+		clientv3.WithPrevKV())
+	resp, ok := <-wch
+	if err := resp.Err(); err != nil || !ok {
+		cancel()
+		return nil, etcdErr.NewError(etcdErr.EcodeRaftInternal, prefix, 0)
+	}
+
+	evc, donec := make(chan *store.Event), make(chan struct{})
+	go func() {
+		defer func() {
+			close(evc)
+			close(donec)
+		}()
+		for resp := range wch {
+			for _, ev := range s.mkV2Events(resp) {
+				k := ev.Node.Key
+				if recursive {
+					if !strings.HasPrefix(k, prefix) {
+						continue
+					}
+					// accept events on hidden keys given in prefix
+					k = strings.Replace(k, prefix, "/", 1)
+					// ignore hidden keys deeper than prefix
+					if strings.Contains(k, "/_") {
+						continue
+					}
+				}
+				if !recursive && k != prefix {
+					continue
+				}
+				select {
+				case evc <- ev:
+				case <-ctx.Done():
+					return
+				}
+				if !stream {
+					return
+				}
+			}
+		}
+	}()
+
+	return &v2v3Watcher{
+		startRev: resp.Header.Revision,
+		evc:      evc,
+		donec:    donec,
+		cancel:   cancel,
+	}, nil
+}
+
+func (s *v2v3Store) mkV2Events(wr clientv3.WatchResponse) (evs []*store.Event) {
+	ak := s.mkActionKey()
+	for _, rev := range mkRevs(wr) {
+		var act, key *clientv3.Event
+		for _, ev := range rev {
+			if string(ev.Kv.Key) == ak {
+				act = ev
+			} else if key != nil && len(key.Kv.Key) < len(ev.Kv.Key) {
+				// use longest key to ignore intermediate new
+				// directories from Create.
+				key = ev
+			} else if key == nil {
+				key = ev
+			}
+		}
+		v2ev := &store.Event{
+			Action:    string(act.Kv.Value),
+			Node:      s.mkV2Node(key.Kv),
+			PrevNode:  s.mkV2Node(key.PrevKv),
+			EtcdIndex: mkV2Rev(wr.Header.Revision),
+		}
+		evs = append(evs, v2ev)
+	}
+	return evs
+}
+
+func mkRevs(wr clientv3.WatchResponse) (revs [][]*clientv3.Event) {
+	var curRev []*clientv3.Event
+	for _, ev := range wr.Events {
+		if curRev != nil && ev.Kv.ModRevision != curRev[0].Kv.ModRevision {
+			revs = append(revs, curRev)
+			curRev = nil
+		}
+		curRev = append(curRev, ev)
+	}
+	if curRev != nil {
+		revs = append(revs, curRev)
+	}
+	return revs
+}
+
+type v2v3Watcher struct {
+	startRev int64
+	evc      chan *store.Event
+	donec    chan struct{}
+	cancel   context.CancelFunc
+}
+
+func (w *v2v3Watcher) StartIndex() uint64 { return mkV2Rev(w.startRev) }
+
+func (w *v2v3Watcher) Remove() {
+	w.cancel()
+	<-w.donec
+}
+
+func (w *v2v3Watcher) EventChan() chan *store.Event { return w.evc }