diff --git a/br/pkg/lightning/backend/local/local.go b/br/pkg/lightning/backend/local/local.go
index ff7d9aa1810c6..bb7f5892b4c57 100644
--- a/br/pkg/lightning/backend/local/local.go
+++ b/br/pkg/lightning/backend/local/local.go
@@ -93,7 +93,7 @@ const (
 	gRPCBackOffMaxDelay  = 10 * time.Minute
 
 	// See: https://github.com/tikv/tikv/blob/e030a0aae9622f3774df89c62f21b2171a72a69e/etc/config-template.toml#L360
-	regionMaxKeyCount      = 1_440_000
+	regionMaxKeyCount      = 1_280_000
 	defaultRegionSplitSize = 96 * units.MiB
 
 	propRangeIndex = "tikv.range_index"
diff --git a/ddl/index.go b/ddl/index.go
index 3e802975cd746..cbfaabf25c25f 100644
--- a/ddl/index.go
+++ b/ddl/index.go
@@ -17,12 +17,13 @@ package ddl
 import (
 	"context"
 	"fmt"
-	"github.com/pingcap/tidb/ddl/sst"
-	"github.com/pingcap/tidb/util/sqlexec"
 	"strings"
 	"sync/atomic"
 	"time"
 
+	"github.com/pingcap/tidb/ddl/sst"
+	"github.com/pingcap/tidb/util/sqlexec"
+
 	tableutil "github.com/pingcap/tidb/table/tables/util"
 
 	"github.com/pingcap/errors"
@@ -555,7 +556,7 @@ func (w *worker) onCreateIndex(d *ddlCtx, t *meta.Meta, job *model.Job, isPK boo
 	case model.StateWriteReorganization:
 		// TODO: optimize index ddl.
 		if *sst.IndexDDLLightning {
-			sst.PrepareIndexOp(w.ctx, sst.DDLInfo{job.SchemaName, tblInfo, job.StartTS})
+			err = sst.PrepareIndexOp(w.ctx, sst.DDLInfo{job.SchemaName, tblInfo, job.StartTS})
 			if err != nil {
 				return ver, errors.Trace(fmt.Errorf("PrepareIndexOp err:%w", err))
 			}
diff --git a/ddl/sst/common.go b/ddl/sst/common.go
index 918c383d46200..f07b0fec297e1 100644
--- a/ddl/sst/common.go
+++ b/ddl/sst/common.go
@@ -10,11 +10,16 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/docker/go-units"
+	sstpb "github.com/pingcap/kvproto/pkg/import_sstpb"
+
 	"github.com/pingcap/tidb/br/pkg/lightning/backend"
 	"github.com/pingcap/tidb/br/pkg/lightning/backend/local"
 	"github.com/pingcap/tidb/br/pkg/lightning/checkpoints"
+	"github.com/pingcap/tidb/br/pkg/lightning/common"
 	"github.com/pingcap/tidb/br/pkg/lightning/config"
 	"github.com/pingcap/tidb/br/pkg/lightning/glue"
+	"github.com/pingcap/tidb/br/pkg/lightning/tikv"
 	"github.com/pingcap/tidb/parser"
 	"github.com/pingcap/tidb/parser/model"
 	"github.com/pingcap/tidb/util/logutil"
@@ -116,7 +121,7 @@ func (_ glue_) Record(string, uint64) {
 }
 
 func generateLightningConfig(info ClusterInfo) *config.Config {
-	cfg := config.Config{}
+	cfg := config.NewConfig()
 	cfg.DefaultVarsForImporterAndLocalBackend()
 	name, err := ioutil.TempDir(*sortkv, "lightning")
 	if err != nil {
@@ -125,14 +130,16 @@ func generateLightningConfig(info ClusterInfo) *config.Config {
 	}
 	os.Remove(name)
 	LogDebug("./ %s.", name)
-	// cfg.TikvImporter.RangeConcurrency = 32
 	cfg.Checkpoint.Enable = false
 	cfg.TikvImporter.SortedKVDir = name
+	cfg.TikvImporter.RangeConcurrency = 32
+	cfg.TikvImporter.EngineMemCacheSize = 512 * units.MiB
+	cfg.TikvImporter.LocalWriterMemCacheSize = 128 * units.MiB
 	cfg.TikvImporter.DuplicateResolution = config.DupeResAlgNone
 	cfg.TiDB.PdAddr = info.PdAddr
 	cfg.TiDB.Host = "127.0.0.1"
 	cfg.TiDB.StatusPort = int(info.Status)
-	return &cfg
+	return cfg
 }
 
 func createLocalBackend(ctx context.Context, info ClusterInfo) (backend.Backend, error) {
@@ -144,3 +151,26 @@ func createLocalBackend(ctx context.Context, info ClusterInfo) (backend.Backend,
 	var g glue_
 	return local.NewLocalBackend(ctx, tls, cfg, &g, int(limit), nil)
 }
+
+func switchTiKVMode(tls *common.TLS, ctx context.Context, mode sstpb.SwitchMode) {
+	// It is fine if we miss some stores which did not switch to Import mode,
+	// since we're running it periodically, so we exclude disconnected stores.
+	// But it is essential all stores be switched back to Normal mode to allow
+	// normal operation.
+	var minState tikv.StoreState
+	if mode == sstpb.SwitchMode_Import {
+		minState = tikv.StoreStateOffline
+	} else {
+		minState = tikv.StoreStateDisconnected
+	}
+	// we ignore switch mode failure since it is not fatal.
+	// no need log the error, it is done in kv.SwitchMode already.
+	_ = tikv.ForAllStores(
+		ctx,
+		tls,
+		minState,
+		func(c context.Context, store *tikv.Store) error {
+			return tikv.SwitchMode(c, tls, store.Address, mode)
+		},
+	)
+}
diff --git a/ddl/sst/index.go b/ddl/sst/index.go
index 91367df6899f6..d3f6724764250 100644
--- a/ddl/sst/index.go
+++ b/ddl/sst/index.go
@@ -6,6 +6,8 @@ import (
 	"encoding/json"
 	"fmt"
 
+	"github.com/pingcap/errors"
+
 	"github.com/pingcap/tidb/br/pkg/lightning/backend/local"
 	"github.com/pingcap/tidb/util/sqlexec"
 
@@ -192,8 +194,14 @@ func FinishIndexOp(ctx context.Context, startTs uint64, exec sqlexec.RestrictedS
 	//
 	closeEngine, err1 := indexEngine.Close(ctx, cfg)
 	if err1 != nil {
-		return fmt.Errorf("engine.Close err:%w", err1)
-	}
+		return errors.Annotate(err1, "engine.Close err")
+	}
+	//tls, err := common.NewTLS("", "", "", cluster.PdAddr)
+	//if err != nil {
+	//	return errors.Annotate(err, "fail to create tls")
+	//}
+	//switchTiKVMode(tls, ctx, sstpb.SwitchMode_Import)
+	//defer switchTiKVMode(tls, ctx, sstpb.SwitchMode_Normal)
 	// use default value first;
 	err = closeEngine.Import(ctx, int64(config.SplitRegionSize))
 	if err != nil {