diff --git a/README.md b/README.md
index d86768a..4376a37 100644
--- a/README.md
+++ b/README.md
@@ -71,3 +71,30 @@
   [blobstore package](https://google.golang.org/appengine/blobstore).
 * `appengine/socket` is not required on App Engine flexible environment / Managed VMs.
   Use the standard `net` package instead.
+
+## Key Encode/Decode compatibiltiy to help with datastore library migrations
+
+Key compatibility updates have been added to help customers transition from google.golang.org/appengine/datastore to cloud.google.com/go/datastore.
+The `EnableKeyConversion` enables automatic conversion from a key encoded with cloud.google.com/go/datastore to google.golang.org/appengine/datastore key type.
+
+### Enabling key conversion
+
+Enable key conversion by calling `EnableKeyConversion(ctx)` in the `/_ah/startup` handler for basic and manual scaling or any handler in automatic scaling.
+
+#### 1. Basic or manual scaling
+
+This startup handler will enable key conversion for all handlers in the service.
+
+```
+http.HandleFunc("/_ah/start", func(w http.ResponseWriter, r *http.Request) {
+    datastore.EnableKeyConversion(appengine.NewContext(r))
+})
+```
+
+#### 2. Automatic scaling
+
+`/_ah/start` is not supported for automatic scaling and `/_ah/warmup` is not guaranteed to run, so you must call `datastore.EnableKeyConversion(appengine.NewContext(r))`
+before you use code that needs key conversion.
+
+You may want to add this to each of your handlers, or introduce middleware where it's called.
+`EnableKeyConversion` is safe for concurrent use. Any call to it after the first is ignored.
\ No newline at end of file
diff --git a/datastore/internal/cloudkey/cloudkey.go b/datastore/internal/cloudkey/cloudkey.go
new file mode 100644
index 0000000..643d404
--- /dev/null
+++ b/datastore/internal/cloudkey/cloudkey.go
@@ -0,0 +1,120 @@
+// Copyright 2019 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+// Package cloudpb is a subset of types and functions, copied from cloud.google.com/go/datastore.
+//
+// They are copied here to provide compatibility to decode keys generated by the cloud.google.com/go/datastore package.
+package cloudkey
+
+import (
+	"encoding/base64"
+	"errors"
+	"strings"
+
+	"github.com/golang/protobuf/proto"
+	cloudpb "google.golang.org/appengine/datastore/internal/cloudpb"
+)
+
+/////////////////////////////////////////////////////////////////////
+// Code below is copied from https://github.com/googleapis/google-cloud-go/blob/master/datastore/datastore.go
+/////////////////////////////////////////////////////////////////////
+
+var (
+	// ErrInvalidKey is returned when an invalid key is presented.
+	ErrInvalidKey = errors.New("datastore: invalid key")
+)
+
+/////////////////////////////////////////////////////////////////////
+// Code below is copied from https://github.com/googleapis/google-cloud-go/blob/master/datastore/key.go
+/////////////////////////////////////////////////////////////////////
+
+// Key represents the datastore key for a stored entity.
+type Key struct {
+	// Kind cannot be empty.
+	Kind string
+	// Either ID or Name must be zero for the Key to be valid.
+	// If both are zero, the Key is incomplete.
+	ID   int64
+	Name string
+	// Parent must either be a complete Key or nil.
+	Parent *Key
+
+	// Namespace provides the ability to partition your data for multiple
+	// tenants. In most cases, it is not necessary to specify a namespace.
+	// See docs on datastore multitenancy for details:
+	// https://cloud.google.com/datastore/docs/concepts/multitenancy
+	Namespace string
+}
+
+// DecodeKey decodes a key from the opaque representation returned by Encode.
+func DecodeKey(encoded string) (*Key, error) {
+	// Re-add padding.
+	if m := len(encoded) % 4; m != 0 {
+		encoded += strings.Repeat("=", 4-m)
+	}
+
+	b, err := base64.URLEncoding.DecodeString(encoded)
+	if err != nil {
+		return nil, err
+	}
+
+	pKey := new(cloudpb.Key)
+	if err := proto.Unmarshal(b, pKey); err != nil {
+		return nil, err
+	}
+	return protoToKey(pKey)
+}
+
+// valid returns whether the key is valid.
+func (k *Key) valid() bool {
+	if k == nil {
+		return false
+	}
+	for ; k != nil; k = k.Parent {
+		if k.Kind == "" {
+			return false
+		}
+		if k.Name != "" && k.ID != 0 {
+			return false
+		}
+		if k.Parent != nil {
+			if k.Parent.Incomplete() {
+				return false
+			}
+			if k.Parent.Namespace != k.Namespace {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// Incomplete reports whether the key does not refer to a stored entity.
+func (k *Key) Incomplete() bool {
+	return k.Name == "" && k.ID == 0
+}
+
+// protoToKey decodes a protocol buffer representation of a key into an
+// equivalent *Key object. If the key is invalid, protoToKey will return the
+// invalid key along with ErrInvalidKey.
+func protoToKey(p *cloudpb.Key) (*Key, error) {
+	var key *Key
+	var namespace string
+	if partition := p.PartitionId; partition != nil {
+		namespace = partition.NamespaceId
+	}
+	for _, el := range p.Path {
+		key = &Key{
+			Namespace: namespace,
+			Kind:      el.Kind,
+			ID:        el.GetId(),
+			Name:      el.GetName(),
+			Parent:    key,
+		}
+	}
+	if !key.valid() { // Also detects key == nil.
+		return key, ErrInvalidKey
+	}
+	return key, nil
+}
diff --git a/datastore/internal/cloudpb/entity.pb.go b/datastore/internal/cloudpb/entity.pb.go
new file mode 100644
index 0000000..af8195f
--- /dev/null
+++ b/datastore/internal/cloudpb/entity.pb.go
@@ -0,0 +1,344 @@
+// Copyright 2019 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+// Package cloudpb is a subset of protobufs, copied from google.golang.org/genproto/googleapis/datastore/v1.
+//
+// They are copied here to provide compatibility to decode keys generated by the cloud.google.com/go/datastore package.
+package cloudpb
+
+import (
+	"fmt"
+
+	"github.com/golang/protobuf/proto"
+)
+
+// A partition ID identifies a grouping of entities. The grouping is always
+// by project and namespace, however the namespace ID may be empty.
+//
+// A partition ID contains several dimensions:
+// project ID and namespace ID.
+//
+// Partition dimensions:
+//
+// - May be `""`.
+// - Must be valid UTF-8 bytes.
+// - Must have values that match regex `[A-Za-z\d\.\-_]{1,100}`
+// If the value of any dimension matches regex `__.*__`, the partition is
+// reserved/read-only.
+// A reserved/read-only partition ID is forbidden in certain documented
+// contexts.
+//
+// Foreign partition IDs (in which the project ID does
+// not match the context project ID ) are discouraged.
+// Reads and writes of foreign partition IDs may fail if the project is not in
+// an active state.
+type PartitionId struct {
+	// The ID of the project to which the entities belong.
+	ProjectId string `protobuf:"bytes,2,opt,name=project_id,json=projectId,proto3" json:"project_id,omitempty"`
+	// If not empty, the ID of the namespace to which the entities belong.
+	NamespaceId          string   `protobuf:"bytes,4,opt,name=namespace_id,json=namespaceId,proto3" json:"namespace_id,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *PartitionId) Reset()         { *m = PartitionId{} }
+func (m *PartitionId) String() string { return proto.CompactTextString(m) }
+func (*PartitionId) ProtoMessage()    {}
+func (*PartitionId) Descriptor() ([]byte, []int) {
+	return fileDescriptor_entity_096a297364b049a5, []int{0}
+}
+func (m *PartitionId) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_PartitionId.Unmarshal(m, b)
+}
+func (m *PartitionId) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_PartitionId.Marshal(b, m, deterministic)
+}
+func (dst *PartitionId) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_PartitionId.Merge(dst, src)
+}
+func (m *PartitionId) XXX_Size() int {
+	return xxx_messageInfo_PartitionId.Size(m)
+}
+func (m *PartitionId) XXX_DiscardUnknown() {
+	xxx_messageInfo_PartitionId.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_PartitionId proto.InternalMessageInfo
+
+func (m *PartitionId) GetProjectId() string {
+	if m != nil {
+		return m.ProjectId
+	}
+	return ""
+}
+
+func (m *PartitionId) GetNamespaceId() string {
+	if m != nil {
+		return m.NamespaceId
+	}
+	return ""
+}
+
+// A unique identifier for an entity.
+// If a key's partition ID or any of its path kinds or names are
+// reserved/read-only, the key is reserved/read-only.
+// A reserved/read-only key is forbidden in certain documented contexts.
+type Key struct {
+	// Entities are partitioned into subsets, currently identified by a project
+	// ID and namespace ID.
+	// Queries are scoped to a single partition.
+	PartitionId *PartitionId `protobuf:"bytes,1,opt,name=partition_id,json=partitionId,proto3" json:"partition_id,omitempty"`
+	// The entity path.
+	// An entity path consists of one or more elements composed of a kind and a
+	// string or numerical identifier, which identify entities. The first
+	// element identifies a _root entity_, the second element identifies
+	// a _child_ of the root entity, the third element identifies a child of the
+	// second entity, and so forth. The entities identified by all prefixes of
+	// the path are called the element's _ancestors_.
+	//
+	// An entity path is always fully complete: *all* of the entity's ancestors
+	// are required to be in the path along with the entity identifier itself.
+	// The only exception is that in some documented cases, the identifier in the
+	// last path element (for the entity) itself may be omitted. For example,
+	// the last path element of the key of `Mutation.insert` may have no
+	// identifier.
+	//
+	// A path can never be empty, and a path can have at most 100 elements.
+	Path                 []*Key_PathElement `protobuf:"bytes,2,rep,name=path,proto3" json:"path,omitempty"`
+	XXX_NoUnkeyedLiteral struct{}           `json:"-"`
+	XXX_unrecognized     []byte             `json:"-"`
+	XXX_sizecache        int32              `json:"-"`
+}
+
+func (m *Key) Reset()         { *m = Key{} }
+func (m *Key) String() string { return proto.CompactTextString(m) }
+func (*Key) ProtoMessage()    {}
+func (*Key) Descriptor() ([]byte, []int) {
+	return fileDescriptor_entity_096a297364b049a5, []int{1}
+}
+func (m *Key) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Key.Unmarshal(m, b)
+}
+func (m *Key) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Key.Marshal(b, m, deterministic)
+}
+func (dst *Key) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Key.Merge(dst, src)
+}
+func (m *Key) XXX_Size() int {
+	return xxx_messageInfo_Key.Size(m)
+}
+func (m *Key) XXX_DiscardUnknown() {
+	xxx_messageInfo_Key.DiscardUnknown(m)
+}
+
+// A (kind, ID/name) pair used to construct a key path.
+//
+// If either name or ID is set, the element is complete.
+// If neither is set, the element is incomplete.
+type Key_PathElement struct {
+	// The kind of the entity.
+	// A kind matching regex `__.*__` is reserved/read-only.
+	// A kind must not contain more than 1500 bytes when UTF-8 encoded.
+	// Cannot be `""`.
+	Kind string `protobuf:"bytes,1,opt,name=kind,proto3" json:"kind,omitempty"`
+	// The type of ID.
+	//
+	// Types that are valid to be assigned to IdType:
+	//	*Key_PathElement_Id
+	//	*Key_PathElement_Name
+	IdType               isKey_PathElement_IdType `protobuf_oneof:"id_type"`
+	XXX_NoUnkeyedLiteral struct{}                 `json:"-"`
+	XXX_unrecognized     []byte                   `json:"-"`
+	XXX_sizecache        int32                    `json:"-"`
+}
+
+func (m *Key_PathElement) Reset()         { *m = Key_PathElement{} }
+func (m *Key_PathElement) String() string { return proto.CompactTextString(m) }
+func (*Key_PathElement) ProtoMessage()    {}
+func (*Key_PathElement) Descriptor() ([]byte, []int) {
+	return fileDescriptor_entity_096a297364b049a5, []int{1, 0}
+}
+func (m *Key_PathElement) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Key_PathElement.Unmarshal(m, b)
+}
+func (m *Key_PathElement) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Key_PathElement.Marshal(b, m, deterministic)
+}
+func (dst *Key_PathElement) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Key_PathElement.Merge(dst, src)
+}
+func (m *Key_PathElement) XXX_Size() int {
+	return xxx_messageInfo_Key_PathElement.Size(m)
+}
+func (m *Key_PathElement) XXX_DiscardUnknown() {
+	xxx_messageInfo_Key_PathElement.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Key_PathElement proto.InternalMessageInfo
+
+func (m *Key_PathElement) GetKind() string {
+	if m != nil {
+		return m.Kind
+	}
+	return ""
+}
+
+type isKey_PathElement_IdType interface {
+	isKey_PathElement_IdType()
+}
+
+type Key_PathElement_Id struct {
+	Id int64 `protobuf:"varint,2,opt,name=id,proto3,oneof"`
+}
+
+type Key_PathElement_Name struct {
+	Name string `protobuf:"bytes,3,opt,name=name,proto3,oneof"`
+}
+
+func (*Key_PathElement_Id) isKey_PathElement_IdType() {}
+
+func (*Key_PathElement_Name) isKey_PathElement_IdType() {}
+
+func (m *Key_PathElement) GetIdType() isKey_PathElement_IdType {
+	if m != nil {
+		return m.IdType
+	}
+	return nil
+}
+
+func (m *Key_PathElement) GetId() int64 {
+	if x, ok := m.GetIdType().(*Key_PathElement_Id); ok {
+		return x.Id
+	}
+	return 0
+}
+
+func (m *Key_PathElement) GetName() string {
+	if x, ok := m.GetIdType().(*Key_PathElement_Name); ok {
+		return x.Name
+	}
+	return ""
+}
+
+// XXX_OneofFuncs is for the internal use of the proto package.
+func (*Key_PathElement) XXX_OneofFuncs() (func(msg proto.Message, b *proto.Buffer) error, func(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error), func(msg proto.Message) (n int), []interface{}) {
+	return _Key_PathElement_OneofMarshaler, _Key_PathElement_OneofUnmarshaler, _Key_PathElement_OneofSizer, []interface{}{
+		(*Key_PathElement_Id)(nil),
+		(*Key_PathElement_Name)(nil),
+	}
+}
+
+func _Key_PathElement_OneofMarshaler(msg proto.Message, b *proto.Buffer) error {
+	m := msg.(*Key_PathElement)
+	// id_type
+	switch x := m.IdType.(type) {
+	case *Key_PathElement_Id:
+		b.EncodeVarint(2<<3 | proto.WireVarint)
+		b.EncodeVarint(uint64(x.Id))
+	case *Key_PathElement_Name:
+		b.EncodeVarint(3<<3 | proto.WireBytes)
+		b.EncodeStringBytes(x.Name)
+	case nil:
+	default:
+		return fmt.Errorf("Key_PathElement.IdType has unexpected type %T", x)
+	}
+	return nil
+}
+
+func _Key_PathElement_OneofUnmarshaler(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error) {
+	m := msg.(*Key_PathElement)
+	switch tag {
+	case 2: // id_type.id
+		if wire != proto.WireVarint {
+			return true, proto.ErrInternalBadWireType
+		}
+		x, err := b.DecodeVarint()
+		m.IdType = &Key_PathElement_Id{int64(x)}
+		return true, err
+	case 3: // id_type.name
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		x, err := b.DecodeStringBytes()
+		m.IdType = &Key_PathElement_Name{x}
+		return true, err
+	default:
+		return false, nil
+	}
+}
+
+func _Key_PathElement_OneofSizer(msg proto.Message) (n int) {
+	m := msg.(*Key_PathElement)
+	// id_type
+	switch x := m.IdType.(type) {
+	case *Key_PathElement_Id:
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(x.Id))
+	case *Key_PathElement_Name:
+		n += 1 // tag and wire
+		n += proto.SizeVarint(uint64(len(x.Name)))
+		n += len(x.Name)
+	case nil:
+	default:
+		panic(fmt.Sprintf("proto: unexpected type %T in oneof", x))
+	}
+	return n
+}
+
+var fileDescriptor_entity_096a297364b049a5 = []byte{
+	// 780 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x7c, 0x94, 0xff, 0x6e, 0xdc, 0x44,
+	0x10, 0xc7, 0xed, 0xbb, 0x5c, 0x1a, 0x8f, 0xdd, 0xa4, 0x6c, 0x2a, 0x61, 0x02, 0x28, 0x26, 0x80,
+	0x74, 0x02, 0xc9, 0x6e, 0xc2, 0x1f, 0x54, 0x14, 0xa4, 0x72, 0x25, 0xe0, 0x28, 0x15, 0x9c, 0x56,
+	0x55, 0x24, 0x50, 0xa4, 0xd3, 0xde, 0x79, 0xeb, 0x2e, 0x67, 0xef, 0x5a, 0xf6, 0x3a, 0xaa, 0xdf,
+	0x05, 0xf1, 0x00, 0x3c, 0x0a, 0x8f, 0x80, 0x78, 0x18, 0xb4, 0x3f, 0xec, 0x0b, 0xed, 0x35, 0xff,
+	0x79, 0x67, 0x3e, 0xdf, 0xd9, 0xef, 0xec, 0xce, 0x1a, 0xa2, 0x5c, 0x88, 0xbc, 0xa0, 0x49, 0x46,
+	0x24, 0x69, 0xa4, 0xa8, 0x69, 0x72, 0x73, 0x9a, 0x50, 0x2e, 0x99, 0xec, 0xe2, 0xaa, 0x16, 0x52,
+	0xa0, 0x43, 0x43, 0xc4, 0x03, 0x11, 0xdf, 0x9c, 0x1e, 0x7d, 0x64, 0x65, 0xa4, 0x62, 0x09, 0xe1,
+	0x5c, 0x48, 0x22, 0x99, 0xe0, 0x8d, 0x91, 0x0c, 0x59, 0xbd, 0x5a, 0xb6, 0x2f, 0x93, 0x46, 0xd6,
+	0xed, 0x4a, 0xda, 0xec, 0xf1, 0x9b, 0x59, 0xc9, 0x4a, 0xda, 0x48, 0x52, 0x56, 0x16, 0x08, 0x2d,
+	0x20, 0xbb, 0x8a, 0x26, 0x05, 0x91, 0x05, 0xcf, 0x4d, 0xe6, 0xe4, 0x17, 0xf0, 0xe7, 0xa4, 0x96,
+	0x4c, 0x6d, 0x76, 0x91, 0xa1, 0x8f, 0x01, 0xaa, 0x5a, 0xfc, 0x4e, 0x57, 0x72, 0xc1, 0xb2, 0x70,
+	0x14, 0xb9, 0x53, 0x0f, 0x7b, 0x36, 0x72, 0x91, 0xa1, 0x4f, 0x20, 0xe0, 0xa4, 0xa4, 0x4d, 0x45,
+	0x56, 0x54, 0x01, 0x3b, 0x1a, 0xf0, 0x87, 0xd8, 0x45, 0x76, 0xf2, 0x8f, 0x0b, 0xe3, 0x4b, 0xda,
+	0xa1, 0x67, 0x10, 0x54, 0x7d, 0x61, 0x85, 0xba, 0x91, 0x3b, 0xf5, 0xcf, 0xa2, 0x78, 0x4b, 0xef,
+	0xf1, 0x2d, 0x07, 0xd8, 0xaf, 0x6e, 0xd9, 0x79, 0x0c, 0x3b, 0x15, 0x91, 0xaf, 0xc2, 0x51, 0x34,
+	0x9e, 0xfa, 0x67, 0x9f, 0x6d, 0x15, 0x5f, 0xd2, 0x2e, 0x9e, 0x13, 0xf9, 0xea, 0xbc, 0xa0, 0x25,
+	0xe5, 0x12, 0x6b, 0xc5, 0xd1, 0x0b, 0xd5, 0xd7, 0x10, 0x44, 0x08, 0x76, 0xd6, 0x8c, 0x1b, 0x17,
+	0x1e, 0xd6, 0xdf, 0xe8, 0x01, 0x8c, 0x6c, 0x8f, 0xe3, 0xd4, 0xc1, 0x23, 0x96, 0xa1, 0x87, 0xb0,
+	0xa3, 0x5a, 0x09, 0xc7, 0x8a, 0x4a, 0x1d, 0xac, 0x57, 0x33, 0x0f, 0xee, 0xb1, 0x6c, 0xa1, 0x8e,
+	0xee, 0xe4, 0x29, 0xc0, 0xf7, 0x75, 0x4d, 0xba, 0x2b, 0x52, 0xb4, 0x14, 0x9d, 0xc1, 0xee, 0x8d,
+	0xfa, 0x68, 0x42, 0x57, 0xfb, 0x3b, 0xda, 0xea, 0x4f, 0xb3, 0xd8, 0x92, 0x27, 0x7f, 0x4c, 0x60,
+	0x62, 0xd4, 0x4f, 0x00, 0x78, 0x5b, 0x14, 0x0b, 0x9d, 0x08, 0xfd, 0xc8, 0x9d, 0xee, 0x6f, 0x2a,
+	0xf4, 0x37, 0x19, 0xff, 0xdc, 0x16, 0x85, 0xe6, 0x53, 0x07, 0x7b, 0xbc, 0x5f, 0xa0, 0xcf, 0xe1,
+	0xfe, 0x52, 0x88, 0x82, 0x12, 0x6e, 0xf5, 0xaa, 0xb1, 0xbd, 0xd4, 0xc1, 0x81, 0x0d, 0x0f, 0x18,
+	0xe3, 0x92, 0xe6, 0xb4, 0xb6, 0x58, 0xdf, 0x6d, 0x60, 0xc3, 0x06, 0xfb, 0x14, 0x82, 0x4c, 0xb4,
+	0xcb, 0x82, 0x5a, 0x4a, 0xf5, 0xef, 0xa6, 0x0e, 0xf6, 0x4d, 0xd4, 0x40, 0xe7, 0x70, 0x30, 0x8c,
+	0x95, 0xe5, 0x40, 0xdf, 0xe9, 0xdb, 0xa6, 0x5f, 0xf4, 0x5c, 0xea, 0xe0, 0xfd, 0x41, 0x64, 0xca,
+	0x7c, 0x0d, 0xde, 0x9a, 0x76, 0xb6, 0xc0, 0x44, 0x17, 0x08, 0xdf, 0x75, 0xaf, 0xa9, 0x83, 0xf7,
+	0xd6, 0xb4, 0x1b, 0x4c, 0x36, 0xb2, 0x66, 0x3c, 0xb7, 0xda, 0xf7, 0xec, 0x25, 0xf9, 0x26, 0x6a,
+	0xa0, 0x63, 0x80, 0x65, 0x21, 0x96, 0x16, 0x41, 0x91, 0x3b, 0x0d, 0xd4, 0xc1, 0xa9, 0x98, 0x01,
+	0xbe, 0x83, 0x83, 0x9c, 0x8a, 0x45, 0x25, 0x18, 0x97, 0x96, 0xda, 0xd3, 0x26, 0x0e, 0x7b, 0x13,
+	0xea, 0xa2, 0xe3, 0xe7, 0x44, 0x3e, 0xe7, 0x79, 0xea, 0xe0, 0xfb, 0x39, 0x15, 0x73, 0x05, 0x1b,
+	0xf9, 0x53, 0x08, 0xcc, 0x53, 0xb6, 0xda, 0x5d, 0xad, 0xfd, 0x70, 0x6b, 0x03, 0xe7, 0x1a, 0x54,
+	0x0e, 0x8d, 0xc4, 0x54, 0x98, 0x81, 0x4f, 0xd4, 0x08, 0xd9, 0x02, 0x9e, 0x2e, 0x70, 0xbc, 0xb5,
+	0xc0, 0x66, 0xd4, 0x52, 0x07, 0x03, 0xd9, 0x0c, 0x5e, 0x08, 0xf7, 0x4a, 0x4a, 0x38, 0xe3, 0x79,
+	0xb8, 0x1f, 0xb9, 0xd3, 0x09, 0xee, 0x97, 0xe8, 0x11, 0x3c, 0xa4, 0xaf, 0x57, 0x45, 0x9b, 0xd1,
+	0xc5, 0xcb, 0x5a, 0x94, 0x0b, 0xc6, 0x33, 0xfa, 0x9a, 0x36, 0xe1, 0xa1, 0x1a, 0x0f, 0x8c, 0x6c,
+	0xee, 0xc7, 0x5a, 0x94, 0x17, 0x26, 0x33, 0x0b, 0x00, 0xb4, 0x13, 0x33, 0xe0, 0xff, 0xba, 0xb0,
+	0x6b, 0x7c, 0xa3, 0x2f, 0x60, 0xbc, 0xa6, 0x9d, 0x7d, 0xb7, 0xef, 0xbc, 0x22, 0xac, 0x20, 0x74,
+	0xa9, 0x7f, 0x1b, 0x15, 0xad, 0x25, 0xa3, 0x4d, 0x38, 0xd6, 0xaf, 0xe1, 0xcb, 0x3b, 0x0e, 0x25,
+	0x9e, 0x0f, 0xf4, 0x39, 0x97, 0x75, 0x87, 0x6f, 0xc9, 0x8f, 0x7e, 0x85, 0x83, 0x37, 0xd2, 0xe8,
+	0xc1, 0xc6, 0x8b, 0x67, 0x76, 0x7c, 0x04, 0x93, 0xcd, 0x44, 0xdf, 0xfd, 0xf4, 0x0c, 0xf8, 0xcd,
+	0xe8, 0xb1, 0x3b, 0xfb, 0xd3, 0x85, 0xf7, 0x57, 0xa2, 0xdc, 0x06, 0xcf, 0x7c, 0x63, 0x6d, 0xae,
+	0x86, 0x78, 0xee, 0xfe, 0xf6, 0xad, 0x65, 0x72, 0x51, 0x10, 0x9e, 0xc7, 0xa2, 0xce, 0x93, 0x9c,
+	0x72, 0x3d, 0xe2, 0x89, 0x49, 0x91, 0x8a, 0x35, 0xff, 0xfb, 0xcb, 0x3f, 0x19, 0x16, 0x7f, 0x8d,
+	0x3e, 0xf8, 0xc9, 0xc8, 0x9f, 0x15, 0xa2, 0xcd, 0xe2, 0x1f, 0x86, 0x8d, 0xae, 0x4e, 0xff, 0xee,
+	0x73, 0xd7, 0x3a, 0x77, 0x3d, 0xe4, 0xae, 0xaf, 0x4e, 0x97, 0xbb, 0x7a, 0x83, 0xaf, 0xfe, 0x0b,
+	0x00, 0x00, 0xff, 0xff, 0xf3, 0xdd, 0x11, 0x96, 0x45, 0x06, 0x00, 0x00,
+}
+
+var xxx_messageInfo_Key proto.InternalMessageInfo
diff --git a/datastore/key.go b/datastore/key.go
index 6ab83ea..fd598dc 100644
--- a/datastore/key.go
+++ b/datastore/key.go
@@ -254,6 +254,10 @@
 
 	ref := new(pb.Reference)
 	if err := proto.Unmarshal(b, ref); err != nil {
+		// Couldn't decode it as an App Engine key, try decoding it as a key encoded by cloud.google.com/go/datastore.
+		if k := decodeCloudKey(encoded); k != nil {
+			return k, nil
+		}
 		return nil, err
 	}
 
diff --git a/datastore/keycompat.go b/datastore/keycompat.go
new file mode 100644
index 0000000..371a64e
--- /dev/null
+++ b/datastore/keycompat.go
@@ -0,0 +1,89 @@
+// Copyright 2019 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package datastore
+
+import (
+	"sync"
+
+	"golang.org/x/net/context"
+
+	"google.golang.org/appengine/datastore/internal/cloudkey"
+	"google.golang.org/appengine/internal"
+)
+
+var keyConversion struct {
+	mu    sync.RWMutex
+	appID string // read using getKeyConversionAppID
+}
+
+// EnableKeyConversion enables encoded key compatibility with the Cloud
+// Datastore client library (cloud.google.com/go/datastore). Encoded keys
+// generated by the Cloud Datastore client library will be decoded into App
+// Engine datastore keys.
+//
+// The context provided must be an App Engine context if running in App Engine
+// first generation runtime. This can be called in the /_ah/start handler. It is
+// safe to call multiple times, and is cheap to call, so can also be inserted as
+// middleware.
+//
+// Enabling key compatibility does not affect the encoding format used by
+// Key.Encode, it only expands the type of keys that are able to be decoded with
+// DecodeKey.
+func EnableKeyConversion(ctx context.Context) {
+	// Only attempt to set appID if it's unset.
+	// If already set, ignore.
+	if getKeyConversionAppID() != "" {
+		return
+	}
+
+	keyConversion.mu.Lock()
+	// Check again to avoid race where another goroutine set appID between the call
+	// to getKeyConversionAppID above and taking the write lock.
+	if keyConversion.appID == "" {
+		keyConversion.appID = internal.FullyQualifiedAppID(ctx)
+	}
+	keyConversion.mu.Unlock()
+}
+
+func getKeyConversionAppID() string {
+	keyConversion.mu.RLock()
+	appID := keyConversion.appID
+	keyConversion.mu.RUnlock()
+	return appID
+}
+
+// decodeCloudKey attempts to decode the given encoded key generated by the
+// Cloud Datastore client library (cloud.google.com/go/datastore), returning nil
+// if the key couldn't be decoded.
+func decodeCloudKey(encoded string) *Key {
+	appID := getKeyConversionAppID()
+	if appID == "" {
+		return nil
+	}
+
+	k, err := cloudkey.DecodeKey(encoded)
+	if err != nil {
+		return nil
+	}
+	return convertCloudKey(k, appID)
+}
+
+// convertCloudKey converts a Cloud Datastore key and converts it to an App
+// Engine Datastore key. Cloud Datastore keys don't include the project/app ID,
+// so we must add it back in.
+func convertCloudKey(key *cloudkey.Key, appID string) *Key {
+	if key == nil {
+		return nil
+	}
+	k := &Key{
+		intID:     key.ID,
+		kind:      key.Kind,
+		namespace: key.Namespace,
+		parent:    convertCloudKey(key.Parent, appID),
+		stringID:  key.Name,
+		appID:     appID,
+	}
+	return k
+}
diff --git a/datastore/keycompat_test.go b/datastore/keycompat_test.go
new file mode 100644
index 0000000..923fdac
--- /dev/null
+++ b/datastore/keycompat_test.go
@@ -0,0 +1,89 @@
+// Copyright 2019 Google Inc. All Rights Reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package datastore
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestKeyConversion(t *testing.T) {
+	var tests = []struct {
+		desc       string
+		key        *Key
+		encodedKey string
+	}{
+		{
+			desc: "A control test for legacy to legacy key conversion int as the key",
+			key: &Key{
+				kind:  "Person",
+				intID: 1,
+				appID: "glibrary",
+			},
+			encodedKey: "aghnbGlicmFyeXIMCxIGUGVyc29uGAEM",
+		},
+		{
+			desc: "A control test for legacy to legacy key conversion string as the key",
+			key: &Key{
+				kind:     "Graph",
+				stringID: "graph:7-day-active",
+				appID:    "glibrary",
+			},
+			encodedKey: "aghnbGlicmFyeXIdCxIFR3JhcGgiEmdyYXBoOjctZGF5LWFjdGl2ZQw",
+		},
+
+		// These are keys encoded with cloud.google.com/go/datastore
+		// Standard int as the key
+		{
+			desc: "Convert new key format to old key with int id",
+			key: &Key{
+				kind:  "WordIndex",
+				intID: 1033,
+				appID: "glibrary",
+			},
+			encodedKey: "Eg4KCVdvcmRJbmRleBCJCA",
+		},
+		// These are keys encoded with cloud.google.com/go/datastore
+		// Standard string
+		{
+			desc: "Convert new key format to old key with string id",
+			key: &Key{
+				kind:     "WordIndex",
+				stringID: "IAmAnID",
+				appID:    "glibrary",
+			},
+			encodedKey: "EhQKCVdvcmRJbmRleBoHSUFtQW5JRA",
+		},
+
+		// These are keys encoded with cloud.google.com/go/datastore
+		// ID String with parent as string
+		{
+			desc: "Convert new key format to old key with string id with a parent",
+			key: &Key{
+				kind:     "WordIndex",
+				stringID: "IAmAnID",
+				appID:    "glibrary",
+				parent: &Key{
+					kind:     "LetterIndex",
+					stringID: "IAmAnotherID",
+					appID:    "glibrary",
+				},
+			},
+			encodedKey: "EhsKC0xldHRlckluZGV4GgxJQW1Bbm90aGVySUQSFAoJV29yZEluZGV4GgdJQW1BbklE",
+		},
+	}
+
+	// Simulate the key converter enablement
+	keyConversion.appID = "glibrary"
+	for _, tc := range tests {
+		dk, err := DecodeKey(tc.encodedKey)
+		if err != nil {
+			t.Fatalf("DecodeKey: %v", err)
+		}
+		if !reflect.DeepEqual(dk, tc.key) {
+			t.Errorf("%s: got %+v, want %+v", tc.desc, dk, tc.key)
+		}
+	}
+}