diff --git a/agent/pkg/agent/agent_pool.go b/agent/pkg/agent/agent_pool.go
index 49c3e6cd..58c61eb0 100644
--- a/agent/pkg/agent/agent_pool.go
+++ b/agent/pkg/agent/agent_pool.go
@@ -1,11 +1,12 @@
 package agent
 
 import (
+
+	"github.com/puzpuzpuz/xsync/v4"
 	"github.com/yusing/go-proxy/internal/common"
-	"github.com/yusing/go-proxy/internal/utils/functional"
 )
 
-var agentPool = functional.NewMapOf[string, *AgentConfig]()
+var agentPool = xsync.NewMap[string, *AgentConfig](xsync.WithPresize(10))
 
 func init() {
 	if common.IsTest {
diff --git a/internal/serialization/serialization.go b/internal/serialization/serialization.go
index e1c10b9c..4efe4e7f 100644
--- a/internal/serialization/serialization.go
+++ b/internal/serialization/serialization.go
@@ -15,7 +15,6 @@ import (
 	"github.com/puzpuzpuz/xsync/v4"
 	"github.com/yusing/go-proxy/internal/gperr"
 	"github.com/yusing/go-proxy/internal/utils"
-	"github.com/yusing/go-proxy/internal/utils/functional"
 	"github.com/yusing/go-proxy/internal/utils/strutils"
 )
 
@@ -565,7 +564,7 @@ func UnmarshalValidateYAMLIntercept[T any](data []byte, target *T, intercept fun
 	return MapUnmarshalValidate(m, target)
 }
 
-func UnmarshalValidateYAMLXSync[V any](data []byte) (_ functional.Map[string, V], err gperr.Error) {
+func UnmarshalValidateYAMLXSync[V any](data []byte) (_ *xsync.Map[string, V], err gperr.Error) {
 	data, err = substituteEnv(data)
 	if err != nil {
 		return
@@ -579,7 +578,11 @@ func UnmarshalValidateYAMLXSync[V any](data []byte) (_ functional.Map[string, V]
 	if err = MapUnmarshalValidate(m, m2); err != nil {
 		return
 	}
-	return functional.NewMapFrom(m2), nil
+	ret := xsync.NewMap[string, V](xsync.WithPresize(len(m)))
+	for k, v := range m2 {
+		ret.Store(k, v)
+	}
+	return ret, nil
 }
 
 func loadSerialized[T any](path string, dst *T, deserialize func(data []byte, dst any) error) error {
diff --git a/internal/utils/functional/map.go b/internal/utils/functional/map.go
deleted file mode 100644
index bbc355a6..00000000
--- a/internal/utils/functional/map.go
+++ /dev/null
@@ -1,103 +0,0 @@
-package functional
-
-import (
-	"sync"
-
-	"github.com/goccy/go-yaml"
-	"github.com/puzpuzpuz/xsync/v4"
-)
-
-type Map[KT comparable, VT any] struct {
-	*xsync.Map[KT, VT]
-}
-
-const minParallelSize = 4
-
-func NewMapOf[KT comparable, VT any](options ...func(*xsync.MapConfig)) Map[KT, VT] {
-	return Map[KT, VT]{xsync.NewMap[KT, VT](options...)}
-}
-
-func NewMapFrom[KT comparable, VT any](m map[KT]VT) (res Map[KT, VT]) {
-	res = NewMapOf[KT, VT](xsync.WithPresize(len(m)))
-	for k, v := range m {
-		res.Store(k, v)
-	}
-	return
-}
-
-func NewMap[MapType Map[KT, VT], KT comparable, VT any]() Map[KT, VT] {
-	return NewMapOf[KT, VT]()
-}
-
-// RangeAll calls the given function for each key-value pair in the map.
-//
-// Parameters:
-//
-//	do: function to call for each key-value pair
-//
-// Returns:
-//
-//	nothing
-func (m Map[KT, VT]) RangeAll(do func(k KT, v VT)) {
-	m.Range(func(k KT, v VT) bool {
-		do(k, v)
-		return true
-	})
-}
-
-// RangeAllParallel calls the given function for each key-value pair in the map,
-// in parallel. The map is not safe for modification from within the function.
-//
-// Parameters:
-//
-//	do: function to call for each key-value pair
-//
-// Returns:
-//
-//	nothing
-func (m Map[KT, VT]) RangeAllParallel(do func(k KT, v VT)) {
-	if m.Size() < minParallelSize {
-		m.RangeAll(do)
-		return
-	}
-
-	var wg sync.WaitGroup
-	for k, v := range m.Range {
-		wg.Add(1)
-		go func(k KT, v VT) {
-			defer wg.Done()
-			do(k, v)
-		}(k, v)
-	}
-	wg.Wait()
-}
-
-// CollectErrors calls the given function for each key-value pair in the map,
-// then returns a slice of errors collected.
-func (m Map[KT, VT]) CollectErrors(do func(k KT, v VT) error) []error {
-	errs := make([]error, 0)
-	m.Range(func(k KT, v VT) bool {
-		if err := do(k, v); err != nil {
-			errs = append(errs, err)
-		}
-		return true
-	})
-	return errs
-}
-
-func (m Map[KT, VT]) Has(k KT) bool {
-	_, ok := m.Load(k)
-	return ok
-}
-
-func (m Map[KT, VT]) String() string {
-	tmp := make(map[KT]VT, m.Size())
-	m.RangeAll(func(k KT, v VT) {
-		tmp[k] = v
-	})
-	data, err := yaml.Marshal(&tmp)
-	if err != nil {
-		return err.Error()
-	}
-	return string(data)
-}
diff --git a/internal/utils/functional/map_test.go b/internal/utils/functional/map_test.go
deleted file mode 100644
index 97152101..00000000
--- a/internal/utils/functional/map_test.go
+++ /dev/null
@@ -1,20 +0,0 @@
-package functional_test
-
-import (
-	"testing"
-
-	. "github.com/yusing/go-proxy/internal/utils/functional"
-	. "github.com/yusing/go-proxy/internal/utils/testing"
-)
-
-func TestNewMapFrom(t *testing.T) {
-	m := NewMapFrom(map[string]int{
-		"a": 1,
-		"b": 2,
-		"c": 3,
-	})
-	ExpectEqual(t, m.Size(), 3)
-	ExpectTrue(t, m.Has("a"))
-	ExpectTrue(t, m.Has("b"))
-	ExpectTrue(t, m.Has("c"))
-}
diff --git a/internal/watcher/health/monitor/last_seen.go b/internal/watcher/health/monitor/last_seen.go
index 36e7cebc..f7c80be6 100644
--- a/internal/watcher/health/monitor/last_seen.go
+++ b/internal/watcher/health/monitor/last_seen.go
@@ -3,10 +3,10 @@ package monitor
 import (
 	"time"
 
-	F "github.com/yusing/go-proxy/internal/utils/functional"
+	"github.com/puzpuzpuz/xsync/v4"
 )
 
-var lastSeenMap = F.NewMapOf[string, time.Time]()
+var lastSeenMap = xsync.NewMap[string, time.Time](xsync.WithPresize(50), xsync.WithGrowOnly())
 
 func SetLastSeen(service string, lastSeen time.Time) {
 	lastSeenMap.Store(service, lastSeen)