diff --git a/command.go b/command.go
index f216f7d..7273089 100644
--- a/command.go
+++ b/command.go
@@ -556,7 +556,7 @@ func loadCommand(writer *resp.Writer, _ []resp.RESP) {
 		writer.WriteError(err)
 		return
 	}
-	writer.WriteBulkString("OK")
+	writer.WriteSString("OK")
 }
 
 func saveCommand(writer *resp.Writer, _ []resp.RESP) {
@@ -564,7 +564,7 @@ func saveCommand(writer *resp.Writer, _ []resp.RESP) {
 		writer.WriteError(err)
 		return
 	}
-	writer.WriteBulkString("OK")
+	writer.WriteSString("OK")
 }
 
 func evalCommand(writer *resp.Writer, args []resp.RESP) {
diff --git a/command_test.go b/command_test.go
index 8b2b558..94ee1af 100644
--- a/command_test.go
+++ b/command_test.go
@@ -488,11 +488,12 @@ func testCommand(t *testing.T, testType string, rdb *redis.Client, sleepFn func(
 			}
 		})
 
-		t.Run("save", func(t *testing.T) {
+		t.Run("save-load", func(t *testing.T) {
 			rdb.FlushDB(ctx)
 			// set key
-			rdb.Set(ctx, "rdb-key1", 123, 0)
-			rdb.Set(ctx, "rdb-key2", 123, time.Minute)
+			rdb.Set(ctx, "rdb-key1", "123", 0)
+			rdb.Set(ctx, "rdb-key2", "234", time.Minute)
+			rdb.Set(ctx, "rdb-key3", "345", 1)
 			rdb.Incr(ctx, "key-incr")
 			rdb.HSet(ctx, "rdb-hash1", "k1", "v1", "k2", "v2")
 			rdb.SAdd(ctx, "rdb-set1", "k1", "k2")
@@ -502,38 +503,61 @@ func testCommand(t *testing.T, testType string, rdb *redis.Client, sleepFn func(
 				rdb.SAdd(ctx, "rdb-set2", key)
 			}
 			rdb.RPush(ctx, "rdb-list1", "k1", "k2", "k3")
+			rdb.ZAdd(ctx, "rdb-zset1",
+				redis.Z{Score: 200, Member: "k2"},
+				redis.Z{Score: 100, Member: "k1"},
+				redis.Z{Score: 300, Member: "k3"})
 
-			res, err := rdb.Save(context.Background()).Result()
-			ast.Nil(err)
+			res, _ := rdb.Save(context.Background()).Result()
 			ast.Equal(res, "OK")
 
-			_, err = rdb.Do(ctx, "load").Result()
+			_, err := rdb.Do(ctx, "load").Result()
 			ast.Nil(err)
+
+			// valid
+			res, _ = rdb.Get(ctx, "rdb-key1").Result()
+			ast.Equal(res, "123")
+			res, _ = rdb.Get(ctx, "rdb-key2").Result()
+			ast.Equal(res, "234")
+			_, err = rdb.Get(ctx, "rdb-key3").Result()
+			ast.Equal(err, redis.Nil)
+
+			res, _ = rdb.Get(ctx, "key-incr").Result()
+			ast.Equal(res, "1")
+
+			resm, _ := rdb.HGetAll(ctx, "rdb-hash1").Result()
+			ast.Equal(resm, map[string]string{"k1": "v1", "k2": "v2"})
+
+			ress, _ := rdb.SMembers(ctx, "rdb-set1").Result()
+			ast.ElementsMatch(ress, []string{"k1", "k2"})
+
+			ress, _ = rdb.LRange(ctx, "rdb-list1", 0, -1).Result()
+			ast.Equal(ress, []string{"k1", "k2", "k3"})
+
+			resz, _ := rdb.ZPopMin(ctx, "rdb-zset1").Result()
+			ast.Equal(resz, []redis.Z{{
+				Member: "k1", Score: 100,
+			}})
 		})
 	}
 
-	t.Run("closed", func(t *testing.T) {
-		err := rdb.Close()
-		ast.Nil(err)
+	t.Run("close", func(t *testing.T) {
+		ast.Nil(rdb.Close())
 	})
 }
 
 func TestConfig(t *testing.T) {
 	ast := assert.New(t)
-
 	cfg, _ := LoadConfig("config.json")
 	ast.Equal(cfg.Port, 6379)
-
 	_, err := LoadConfig("not-exist.json")
 	ast.NotNil(err)
-
 	_, err = LoadConfig("go.mod")
 	ast.NotNil(err)
 }
 
 func TestReadableSize(t *testing.T) {
 	ast := assert.New(t)
-
 	ast.Equal(readableSize(50), "50B")
 	ast.Equal(readableSize(50*KB), "50.0KB")
 	ast.Equal(readableSize(50*MB), "50.0MB")
diff --git a/const.go b/const.go
index c944d53..8ce8bdd 100644
--- a/const.go
+++ b/const.go
@@ -4,13 +4,14 @@ import (
 	"github.com/xgzlucario/rotom/internal/hash"
 	"github.com/xgzlucario/rotom/internal/iface"
 	"github.com/xgzlucario/rotom/internal/list"
+	"github.com/xgzlucario/rotom/internal/zset"
 )
 
 type ObjectType byte
 
 const (
 	TypeUnknown ObjectType = iota
-	TypeString  ObjectType = iota
+	TypeString
 	TypeInteger
 	TypeMap
 	TypeZipMap
@@ -32,4 +33,5 @@ var type2c = map[ObjectType]func() iface.Encoder{
 	TypeSet:    func() iface.Encoder { return hash.NewSet() },
 	TypeZipSet: func() iface.Encoder { return hash.NewZipSet() },
 	TypeList:   func() iface.Encoder { return list.New() },
+	TypeZSet:   func() iface.Encoder { return zset.New() },
 }
diff --git a/go.mod b/go.mod
index 93cc5c1..dc6686c 100644
--- a/go.mod
+++ b/go.mod
@@ -14,7 +14,7 @@ require (
 	github.com/yuin/gopher-lua v1.1.1
 	github.com/zyedidia/generic v1.2.1
 	golang.org/x/exp v0.0.0-20241009180824-f66d83c29e7c
-	golang.org/x/sys v0.26.0
+	golang.org/x/sys v0.27.0
 )
 
 require (
@@ -33,7 +33,7 @@ require (
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/rogpeppe/go-internal v1.13.1 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
-	golang.org/x/arch v0.11.0 // indirect
+	golang.org/x/arch v0.12.0 // indirect
 	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
diff --git a/go.sum b/go.sum
index 44c6f9b..7bd61af 100644
--- a/go.sum
+++ b/go.sum
@@ -78,16 +78,16 @@ github.com/yuin/gopher-lua v1.1.1 h1:kYKnWBjvbNP4XLT3+bPEwAXJx262OhaHDWDVOPjL46M
 github.com/yuin/gopher-lua v1.1.1/go.mod h1:GBR0iDaNXjAgGg9zfCvksxSRnQx76gclCIb7kdAd1Pw=
 github.com/zyedidia/generic v1.2.1 h1:Zv5KS/N2m0XZZiuLS82qheRG4X1o5gsWreGb0hR7XDc=
 github.com/zyedidia/generic v1.2.1/go.mod h1:ly2RBz4mnz1yeuVbQA/VFwGjK3mnHGRj1JuoG336Bis=
-golang.org/x/arch v0.11.0 h1:KXV8WWKCXm6tRpLirl2szsO5j/oOODwZf4hATmGVNs4=
-golang.org/x/arch v0.11.0/go.mod h1:FEVrYAQjsQXMVJ1nsMoVVXPZg6p2JE2mx8psSWTDQys=
+golang.org/x/arch v0.12.0 h1:UsYJhbzPYGsT0HbEdmYcqtCv8UNGvnaL561NnIUvaKg=
+golang.org/x/arch v0.12.0/go.mod h1:FEVrYAQjsQXMVJ1nsMoVVXPZg6p2JE2mx8psSWTDQys=
 golang.org/x/exp v0.0.0-20241009180824-f66d83c29e7c h1:7dEasQXItcW1xKJ2+gg5VOiBnqWrJc+rq0DPKyvvdbY=
 golang.org/x/exp v0.0.0-20241009180824-f66d83c29e7c/go.mod h1:NQtJDoLvd6faHhE7m4T/1IY708gDefGGjR/iUW8yQQ8=
 golang.org/x/sys v0.0.0-20211216021012-1d35b9e2eb4e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.26.0 h1:KHjCJyddX0LoSTb3J+vWpupP9p0oznkqVk/IfjymZbo=
-golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.27.0 h1:wBqf8DvsY9Y/2P8gAfPDEYNuS30J4lPHJxXSb/nJZ+s=
+golang.org/x/sys v0.27.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
diff --git a/internal/list/list.go b/internal/list/list.go
index f13ce26..0e02aae 100644
--- a/internal/list/list.go
+++ b/internal/list/list.go
@@ -1,10 +1,16 @@
 package list
 
 import (
+	"github.com/xgzlucario/rotom/internal/iface"
 	"github.com/xgzlucario/rotom/internal/resp"
 	"github.com/zyedidia/generic/list"
 )
 
+var (
+	_ iface.Encoder = (*ListPack)(nil)
+	_ iface.Encoder = (*QuickList)(nil)
+)
+
 //	 +------------------------------ QuickList -----------------------------+
 //	 |	     +-----------+     +-----------+             +-----------+      |
 //	head --- | listpack0 | <-> | listpack1 | <-> ... <-> | listpackN | --- tail
diff --git a/internal/resp/resp.go b/internal/resp/resp.go
index 4b8d092..9a33279 100644
--- a/internal/resp/resp.go
+++ b/internal/resp/resp.go
@@ -115,6 +115,14 @@ func (r *Reader) ReadInteger() (int, error) {
 	return r.readInteger()
 }
 
+func (r *Reader) ReadFloat() (float64, error) {
+	buf, err := r.ReadBulk()
+	if err != nil {
+		return 0, nil
+	}
+	return strconv.ParseFloat(b2s(buf), 64)
+}
+
 func (r *Reader) ReadBulk() ([]byte, error) {
 	if len(r.b) == 0 || r.b[0] != BULK {
 		return nil, errors.New("command is not begin with BULK")
diff --git a/internal/zset/zset.go b/internal/zset/zset.go
index 7ced762..ea32dc9 100644
--- a/internal/zset/zset.go
+++ b/internal/zset/zset.go
@@ -2,11 +2,16 @@ package zset
 
 import (
 	"cmp"
-	"github.com/bytedance/sonic"
+	"github.com/xgzlucario/rotom/internal/iface"
+	"github.com/xgzlucario/rotom/internal/resp"
 
 	"github.com/chen3feng/stl4go"
 )
 
+var (
+	_ iface.Encoder = (*ZSet)(nil)
+)
+
 type node struct {
 	key   string
 	score float64
@@ -99,17 +104,32 @@ func (z *ZSet) Len() int {
 	return len(z.m)
 }
 
-func (z *ZSet) Marshal() ([]byte, error) {
-	return sonic.Marshal(z.m)
+func (z *ZSet) Encode(writer *resp.Writer) error {
+	writer.WriteArrayHead(z.Len())
+	for k, s := range z.m {
+		writer.WriteBulkString(k)
+		writer.WriteFloat(s)
+	}
+	return nil
 }
 
-func (z *ZSet) Unmarshal(src []byte) error {
-	err := sonic.Unmarshal(src, &z.m)
+func (z *ZSet) Decode(reader *resp.Reader) error {
+	n, err := reader.ReadArrayHead()
 	if err != nil {
 		return err
 	}
-	for k, v := range z.m {
-		z.skl.Insert(node{k, v}, struct{}{})
+	for range n {
+		buf, err := reader.ReadBulk()
+		if err != nil {
+			return err
+		}
+		score, err := reader.ReadFloat()
+		if err != nil {
+			return err
+		}
+		key := string(buf)
+		z.skl.Insert(node{key, score}, struct{}{})
+		z.m[key] = score
 	}
 	return nil
 }
diff --git a/rdb.go b/rdb.go
index f4bc853..6eee2a0 100644
--- a/rdb.go
+++ b/rdb.go
@@ -1,7 +1,6 @@
 package main
 
 import (
-	"errors"
 	"fmt"
 	"github.com/tidwall/mmap"
 	"github.com/xgzlucario/rotom/internal/iface"
@@ -40,23 +39,11 @@ func (r *Rdb) SaveDB() error {
 
 		switch objectType {
 		case TypeString:
-			raw, ok := v.([]byte)
-			if !ok {
-				return errors.New("invalid data typeString")
-			}
-			writer.WriteBulk(raw)
+			writer.WriteBulk(v.([]byte))
 		case TypeInteger:
-			raw, ok := v.(int)
-			if !ok {
-				return errors.New("invalid data typeInteger")
-			}
-			writer.WriteInteger(raw)
+			writer.WriteInteger(v.(int))
 		default:
-			val, ok := v.(iface.Encoder)
-			if !ok {
-				return errors.New("invalid data type")
-			}
-			if err := val.Encode(writer); err != nil {
+			if err = v.(iface.Encoder).Encode(writer); err != nil {
 				return err
 			}
 		}
@@ -75,15 +62,8 @@ func (r *Rdb) SaveDB() error {
 }
 
 func (r *Rdb) LoadDB() error {
-	fs, err := os.OpenFile(r.path, os.O_RDWR, 0644)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return nil
-		}
-		return err
-	}
 	// Read file data by mmap.
-	data, err := mmap.MapFile(fs, false)
+	data, err := mmap.Open(r.path, false)
 	if len(data) == 0 {
 		return nil
 	}
@@ -92,12 +72,12 @@ func (r *Rdb) LoadDB() error {
 	}
 
 	reader := resp.NewReader(data)
-	count, err := reader.ReadArrayHead()
+	n, err := reader.ReadArrayHead()
 	if err != nil {
 		return err
 	}
 
-	for range count {
+	for range n {
 		// format: {objectType,ttl,key,value}
 		objectType, err := reader.ReadInteger()
 		if err != nil {
@@ -129,10 +109,7 @@ func (r *Rdb) LoadDB() error {
 
 		default:
 			val := type2c[ObjectType(objectType)]()
-			if val == nil {
-				return errors.New("invalid data type")
-			}
-			if err := val.Decode(reader); err != nil {
+			if err = val.Decode(reader); err != nil {
 				return err
 			}
 			db.dict.Set(string(key), val)
diff --git a/rotom.go b/rotom.go
index 30c7a3c..c0e7e18 100644
--- a/rotom.go
+++ b/rotom.go
@@ -116,14 +116,13 @@ func AcceptHandler(loop *AeLoop, fd int, _ interface{}) {
 		log.Error().Msgf("accept err: %v", err)
 		return
 	}
-	// create client
+	log.Info().Msgf("accept new client fd: %d", fd)
 	client := &Client{
 		fd:          cfd,
 		replyWriter: resp.NewWriter(WriteBufSize),
 		queryBuf:    make([]byte, QueryBufSize),
 		argsBuf:     make([]resp.RESP, 8),
 	}
-
 	server.clients[cfd] = client
 	loop.AddRead(cfd, ReadQueryFromClient, client)
 }