diff --git a/server/etcdserver/apply.go b/server/etcdserver/apply.go
index 5ccda706f..ac2d33815 100644
--- a/server/etcdserver/apply.go
+++ b/server/etcdserver/apply.go
@@ -27,6 +27,7 @@ import (
 	"go.etcd.io/etcd/server/v3/etcdserver/api/membership"
 	"go.etcd.io/etcd/server/v3/etcdserver/api/v3alarm"
 	"go.etcd.io/etcd/server/v3/etcdserver/cindex"
+	mvcc_txn "go.etcd.io/etcd/server/v3/etcdserver/txn"
 	"go.etcd.io/etcd/server/v3/etcdserver/version"
 	"go.etcd.io/etcd/server/v3/lease"
 	serverstorage "go.etcd.io/etcd/server/v3/storage"
@@ -145,19 +146,19 @@ func (a *applierV3backend) WrapApply(ctx context.Context, r *pb.InternalRaftRequ
 }
 
 func (a *applierV3backend) Put(ctx context.Context, txn mvcc.TxnWrite, p *pb.PutRequest) (resp *pb.PutResponse, trace *traceutil.Trace, err error) {
-	return Put(ctx, a.lg, a.lessor, a.kv, txn, p)
+	return mvcc_txn.Put(ctx, a.lg, a.lessor, a.kv, txn, p)
 }
 
 func (a *applierV3backend) DeleteRange(txn mvcc.TxnWrite, dr *pb.DeleteRangeRequest) (*pb.DeleteRangeResponse, error) {
-	return DeleteRange(a.kv, txn, dr)
+	return mvcc_txn.DeleteRange(a.kv, txn, dr)
 }
 
 func (a *applierV3backend) Range(ctx context.Context, txn mvcc.TxnRead, r *pb.RangeRequest) (*pb.RangeResponse, error) {
-	return Range(ctx, a.lg, a.kv, txn, r)
+	return mvcc_txn.Range(ctx, a.lg, a.kv, txn, r)
 }
 
 func (a *applierV3backend) Txn(ctx context.Context, rt *pb.TxnRequest) (*pb.TxnResponse, *traceutil.Trace, error) {
-	return Txn(ctx, a.lg, rt, a.txnModeWriteWithSharedBuffer, a.kv, a.lessor)
+	return mvcc_txn.Txn(ctx, a.lg, rt, a.txnModeWriteWithSharedBuffer, a.kv, a.lessor)
 }
 
 func (a *applierV3backend) Compaction(compaction *pb.CompactionRequest) (*pb.CompactionResponse, <-chan struct{}, *traceutil.Trace, error) {
diff --git a/server/etcdserver/errors.go b/server/etcdserver/errors.go
index e28f49c17..aa74739d8 100644
--- a/server/etcdserver/errors.go
+++ b/server/etcdserver/errors.go
@@ -17,6 +17,8 @@ package etcdserver
 import (
 	"errors"
 	"fmt"
+
+	"go.etcd.io/etcd/server/v3/etcdserver/txn"
 )
 
 var (
@@ -37,11 +39,11 @@ var (
 	ErrNoSpace                     = errors.New("etcdserver: no space")
 	ErrTooManyRequests             = errors.New("etcdserver: too many requests")
 	ErrUnhealthy                   = errors.New("etcdserver: unhealthy cluster")
-	ErrKeyNotFound                 = errors.New("etcdserver: key not found")
 	ErrCorrupt                     = errors.New("etcdserver: corrupt cluster")
 	ErrBadLeaderTransferee         = errors.New("etcdserver: bad leader transferee")
 	ErrClusterVersionUnavailable   = errors.New("etcdserver: cluster version not found during downgrade")
 	ErrWrongDowngradeVersionFormat = errors.New("etcdserver: wrong downgrade target version format")
+	ErrKeyNotFound                 = txn.ErrKeyNotFound
 )
 
 type DiscoveryError struct {
diff --git a/server/etcdserver/txn.go b/server/etcdserver/txn/txn.go
similarity index 96%
rename from server/etcdserver/txn.go
rename to server/etcdserver/txn/txn.go
index 747017093..3a5c2debf 100644
--- a/server/etcdserver/txn.go
+++ b/server/etcdserver/txn/txn.go
@@ -12,11 +12,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package etcdserver
+package txn
 
 import (
 	"bytes"
 	"context"
+	"errors"
 	"sort"
 
 	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
@@ -27,6 +28,10 @@ import (
 	"go.uber.org/zap"
 )
 
+var (
+	ErrKeyNotFound = errors.New("etcdserver: key not found")
+)
+
 func Put(ctx context.Context, lg *zap.Logger, lessor lease.Lessor, kv mvcc.KV, txn mvcc.TxnWrite, p *pb.PutRequest) (resp *pb.PutResponse, trace *traceutil.Trace, err error) {
 	resp = &pb.PutResponse{}
 	resp.Header = &pb.ResponseHeader{}
@@ -221,7 +226,7 @@ func Txn(ctx context.Context, lg *zap.Logger, rt *pb.TxnRequest, txnModeWriteWit
 		trace = traceutil.New("transaction", lg)
 		ctx = context.WithValue(ctx, traceutil.TraceKey, trace)
 	}
-	isWrite := !isTxnReadonly(rt)
+	isWrite := !IsTxnReadonly(rt)
 
 	// When the transaction contains write operations, we use ReadTx instead of
 	// ConcurrentReadTx to avoid extra overhead of copying buffer.
@@ -595,3 +600,31 @@ func compareKV(c *pb.Compare, ckv mvccpb.KeyValue) bool {
 	}
 	return true
 }
+
+func IsTxnSerializable(r *pb.TxnRequest) bool {
+	for _, u := range r.Success {
+		if r := u.GetRequestRange(); r == nil || !r.Serializable {
+			return false
+		}
+	}
+	for _, u := range r.Failure {
+		if r := u.GetRequestRange(); r == nil || !r.Serializable {
+			return false
+		}
+	}
+	return true
+}
+
+func IsTxnReadonly(r *pb.TxnRequest) bool {
+	for _, u := range r.Success {
+		if r := u.GetRequestRange(); r == nil {
+			return false
+		}
+	}
+	for _, u := range r.Failure {
+		if r := u.GetRequestRange(); r == nil {
+			return false
+		}
+	}
+	return true
+}
diff --git a/server/etcdserver/v3_server.go b/server/etcdserver/v3_server.go
index bc35c2eff..583ffa387 100644
--- a/server/etcdserver/v3_server.go
+++ b/server/etcdserver/v3_server.go
@@ -28,6 +28,7 @@ import (
 	"go.etcd.io/etcd/raft/v3"
 	"go.etcd.io/etcd/server/v3/auth"
 	"go.etcd.io/etcd/server/v3/etcdserver/api/membership"
+	"go.etcd.io/etcd/server/v3/etcdserver/txn"
 	"go.etcd.io/etcd/server/v3/lease"
 	"go.etcd.io/etcd/server/v3/lease/leasehttp"
 	"go.etcd.io/etcd/server/v3/storage/mvcc"
@@ -128,7 +129,7 @@ func (s *EtcdServer) Range(ctx context.Context, r *pb.RangeRequest) (*pb.RangeRe
 		return s.authStore.IsRangePermitted(ai, r.Key, r.RangeEnd)
 	}
 
-	get := func() { resp, err = Range(ctx, s.Logger(), s.KV(), nil, r) }
+	get := func() { resp, err = txn.Range(ctx, s.Logger(), s.KV(), nil, r) }
 	if serr := s.doSerialize(ctx, chk, get); serr != nil {
 		err = serr
 		return nil, err
@@ -154,13 +155,13 @@ func (s *EtcdServer) DeleteRange(ctx context.Context, r *pb.DeleteRangeRequest)
 }
 
 func (s *EtcdServer) Txn(ctx context.Context, r *pb.TxnRequest) (*pb.TxnResponse, error) {
-	if isTxnReadonly(r) {
+	if txn.IsTxnReadonly(r) {
 		trace := traceutil.New("transaction",
 			s.Logger(),
 			traceutil.Field{Key: "read_only", Value: true},
 		)
 		ctx = context.WithValue(ctx, traceutil.TraceKey, trace)
-		if !isTxnSerializable(r) {
+		if !txn.IsTxnSerializable(r) {
 			err := s.linearizableReadNotify(ctx)
 			trace.Step("agreement among raft nodes before linearized reading")
 			if err != nil {
@@ -179,7 +180,7 @@ func (s *EtcdServer) Txn(ctx context.Context, r *pb.TxnRequest) (*pb.TxnResponse
 		}(time.Now())
 
 		get := func() {
-			resp, _, err = Txn(ctx, s.Logger(), r, s.Cfg.ExperimentalTxnModeWriteWithSharedBuffer, s.KV(), s.lessor)
+			resp, _, err = txn.Txn(ctx, s.Logger(), r, s.Cfg.ExperimentalTxnModeWriteWithSharedBuffer, s.KV(), s.lessor)
 		}
 		if serr := s.doSerialize(ctx, chk, get); serr != nil {
 			return nil, serr
@@ -195,34 +196,6 @@ func (s *EtcdServer) Txn(ctx context.Context, r *pb.TxnRequest) (*pb.TxnResponse
 	return resp.(*pb.TxnResponse), nil
 }
 
-func isTxnSerializable(r *pb.TxnRequest) bool {
-	for _, u := range r.Success {
-		if r := u.GetRequestRange(); r == nil || !r.Serializable {
-			return false
-		}
-	}
-	for _, u := range r.Failure {
-		if r := u.GetRequestRange(); r == nil || !r.Serializable {
-			return false
-		}
-	}
-	return true
-}
-
-func isTxnReadonly(r *pb.TxnRequest) bool {
-	for _, u := range r.Success {
-		if r := u.GetRequestRange(); r == nil {
-			return false
-		}
-	}
-	for _, u := range r.Failure {
-		if r := u.GetRequestRange(); r == nil {
-			return false
-		}
-	}
-	return true
-}
-
 func (s *EtcdServer) Compact(ctx context.Context, r *pb.CompactionRequest) (*pb.CompactionResponse, error) {
 	startTime := time.Now()
 	result, err := s.processInternalRaftRequestOnce(ctx, pb.InternalRaftRequest{Compaction: r})