diff --git a/pkg/mock/mockcluster/mockcluster.go b/pkg/mock/mockcluster/mockcluster.go
index bd0c63f639d..41f3519e779 100644
--- a/pkg/mock/mockcluster/mockcluster.go
+++ b/pkg/mock/mockcluster/mockcluster.go
@@ -389,7 +389,7 @@ func (mc *Cluster) AddRegionWithReadInfo(
 	r = r.Clone(core.SetReadKeys(readKeys))
 	r = r.Clone(core.SetReportInterval(0, reportInterval))
 	r = r.Clone(core.SetReadQuery(readQuery))
-	filledNum := mc.HotCache.GetFilledPeriod(statistics.Read)
+	filledNum := statistics.DefaultAotSize
 	if len(filledNums) > 0 {
 		filledNum = filledNums[0]
 	}
@@ -410,7 +410,7 @@ func (mc *Cluster) AddRegionWithPeerReadInfo(regionID, leaderStoreID, targetStor
 	otherPeerStoreIDs []uint64, filledNums ...int) []*statistics.HotPeerStat {
 	r := mc.newMockRegionInfo(regionID, leaderStoreID, otherPeerStoreIDs...)
 	r = r.Clone(core.SetReadBytes(readBytes), core.SetReadKeys(readKeys), core.SetReportInterval(0, reportInterval))
-	filledNum := mc.HotCache.GetFilledPeriod(statistics.Read)
+	filledNum := statistics.DefaultAotSize
 	if len(filledNums) > 0 {
 		filledNum = filledNums[0]
 	}
@@ -438,7 +438,7 @@ func (mc *Cluster) AddRegionLeaderWithReadInfo(
 	r = r.Clone(core.SetReadKeys(readKeys))
 	r = r.Clone(core.SetReadQuery(readQuery))
 	r = r.Clone(core.SetReportInterval(0, reportInterval))
-	filledNum := mc.HotCache.GetFilledPeriod(statistics.Read)
+	filledNum := statistics.DefaultAotSize
 	if len(filledNums) > 0 {
 		filledNum = filledNums[0]
 	}
@@ -466,7 +466,7 @@ func (mc *Cluster) AddLeaderRegionWithWriteInfo(
 	r = r.Clone(core.SetReportInterval(0, reportInterval))
 	r = r.Clone(core.SetWrittenQuery(writtenQuery))
 
-	filledNum := mc.HotCache.GetFilledPeriod(statistics.Write)
+	filledNum := statistics.DefaultAotSize
 	if len(filledNums) > 0 {
 		filledNum = filledNums[0]
 	}
diff --git a/pkg/movingaverage/avg_over_time.go b/pkg/movingaverage/avg_over_time.go
index 12a6a4b25c2..227ee32e8c7 100644
--- a/pkg/movingaverage/avg_over_time.go
+++ b/pkg/movingaverage/avg_over_time.go
@@ -131,3 +131,11 @@ func (aot *AvgOverTime) Clone() *AvgOverTime {
 func (aot *AvgOverTime) GetIntervalSum() time.Duration {
 	return aot.intervalSum
 }
+
+// GetInstantaneous returns the value just added.
+func (aot *AvgOverTime) GetInstantaneous() float64 {
+	if aot.que.Len() == 0 || aot.que.Back() == nil {
+		return 0
+	}
+	return aot.que.Back().(deltaWithInterval).delta
+}
diff --git a/pkg/movingaverage/avg_over_time_test.go b/pkg/movingaverage/avg_over_time_test.go
index 13b7da27aef..a0787f5af81 100644
--- a/pkg/movingaverage/avg_over_time_test.go
+++ b/pkg/movingaverage/avg_over_time_test.go
@@ -84,7 +84,7 @@ func TestMinFilled(t *testing.T) {
 	for aotSize := 2; aotSize < 10; aotSize++ {
 		for mfSize := 2; mfSize < 10; mfSize++ {
 			tm := NewTimeMedian(aotSize, mfSize, interval)
-			for i := 0; i < tm.GetFilledPeriod(); i++ {
+			for i := 0; i < aotSize; i++ {
 				re.Equal(0.0, tm.Get())
 				tm.Add(rate*interval.Seconds(), interval)
 			}
diff --git a/pkg/movingaverage/median_filter.go b/pkg/movingaverage/median_filter.go
index 5195f0c9253..7041ae53b29 100644
--- a/pkg/movingaverage/median_filter.go
+++ b/pkg/movingaverage/median_filter.go
@@ -23,12 +23,11 @@ type MedianFilter struct {
 	// It is not thread safe to read and write records at the same time.
 	// If there are concurrent read and write, the read may get an old value.
 	// And we should avoid concurrent write.
-	records       []float64
-	size          uint64
-	count         uint64
-	instantaneous float64
-	isUpdated     bool
-	result        float64
+	records   []float64
+	size      uint64
+	count     uint64
+	isUpdated bool
+	result    float64
 }
 
 // NewMedianFilter returns a MedianFilter.
@@ -43,7 +42,6 @@ func NewMedianFilter(size int) *MedianFilter {
 
 // Add adds a data point.
 func (r *MedianFilter) Add(n float64) {
-	r.instantaneous = n
 	r.records[r.count%r.size] = n
 	r.count++
 	r.isUpdated = true
@@ -68,14 +66,12 @@ func (r *MedianFilter) Get() float64 {
 
 // Reset cleans the data set.
 func (r *MedianFilter) Reset() {
-	r.instantaneous = 0
 	r.count = 0
 	r.isUpdated = true
 }
 
 // Set = Reset + Add.
 func (r *MedianFilter) Set(n float64) {
-	r.instantaneous = n
 	r.records[0] = n
 	r.count = 1
 	r.isUpdated = true
@@ -83,7 +79,7 @@ func (r *MedianFilter) Set(n float64) {
 
 // GetInstantaneous returns the value just added.
 func (r *MedianFilter) GetInstantaneous() float64 {
-	return r.instantaneous
+	return r.records[(r.count-1)%r.size]
 }
 
 // Clone returns a copy of MedianFilter
@@ -91,11 +87,10 @@ func (r *MedianFilter) Clone() *MedianFilter {
 	records := make([]float64, len(r.records))
 	copy(records, r.records)
 	return &MedianFilter{
-		records:       records,
-		size:          r.size,
-		count:         r.count,
-		instantaneous: r.instantaneous,
-		isUpdated:     r.isUpdated,
-		result:        r.result,
+		records:   records,
+		size:      r.size,
+		count:     r.count,
+		isUpdated: r.isUpdated,
+		result:    r.result,
 	}
 }
diff --git a/pkg/movingaverage/moving_average_test.go b/pkg/movingaverage/moving_average_test.go
index 173eea773bb..37aaba28e47 100644
--- a/pkg/movingaverage/moving_average_test.go
+++ b/pkg/movingaverage/moving_average_test.go
@@ -43,6 +43,7 @@ func checkAdd(re *require.Assertions, ma MovingAvg, data []float64, expected []f
 	re.Len(data, len(expected))
 	for i, x := range data {
 		ma.Add(x)
+		re.Equal(x, ma.GetInstantaneous())
 		re.LessOrEqual(math.Abs(ma.Get()-expected[i]), 1e-7)
 	}
 }
diff --git a/pkg/movingaverage/time_median.go b/pkg/movingaverage/time_median.go
index 1c9f9595f35..88ad562a3cf 100644
--- a/pkg/movingaverage/time_median.go
+++ b/pkg/movingaverage/time_median.go
@@ -21,20 +21,15 @@ import "time"
 // Delay is aotSize * mfSize * reportInterval/4
 // and the min filled period is aotSize * reportInterval, which is not related with mfSize
 type TimeMedian struct {
-	aot           *AvgOverTime
-	mf            *MedianFilter
-	aotSize       int
-	mfSize        int
-	instantaneous float64
+	aot *AvgOverTime
+	mf  *MedianFilter
 }
 
 // NewTimeMedian returns a TimeMedian with given size.
 func NewTimeMedian(aotSize, mfSize int, reportInterval time.Duration) *TimeMedian {
 	return &TimeMedian{
-		aot:     NewAvgOverTime(time.Duration(aotSize) * reportInterval),
-		mf:      NewMedianFilter(mfSize),
-		aotSize: aotSize,
-		mfSize:  mfSize,
+		aot: NewAvgOverTime(time.Duration(aotSize) * reportInterval),
+		mf:  NewMedianFilter(mfSize),
 	}
 }
 
@@ -45,7 +40,6 @@ func (t *TimeMedian) Get() float64 {
 
 // Add adds recent change to TimeMedian.
 func (t *TimeMedian) Add(delta float64, interval time.Duration) {
-	t.instantaneous = delta / interval.Seconds()
 	t.aot.Add(delta, interval)
 	if t.aot.IsFull() {
 		t.mf.Add(t.aot.Get())
@@ -57,23 +51,15 @@ func (t *TimeMedian) Set(avg float64) {
 	t.mf.Set(avg)
 }
 
-// GetFilledPeriod returns filled period.
-func (t *TimeMedian) GetFilledPeriod() int { // it is unrelated with mfSize
-	return t.aotSize
-}
-
 // GetInstantaneous returns instantaneous speed
 func (t *TimeMedian) GetInstantaneous() float64 {
-	return t.instantaneous
+	return t.aot.GetInstantaneous()
 }
 
 // Clone returns a copy of TimeMedian
 func (t *TimeMedian) Clone() *TimeMedian {
 	return &TimeMedian{
-		aot:           t.aot.Clone(),
-		mf:            t.mf.Clone(),
-		aotSize:       t.aotSize,
-		mfSize:        t.mfSize,
-		instantaneous: t.instantaneous,
+		aot: t.aot.Clone(),
+		mf:  t.mf.Clone(),
 	}
 }
diff --git a/server/statistics/hot_cache.go b/server/statistics/hot_cache.go
index 66121e8d026..464c937a874 100644
--- a/server/statistics/hot_cache.go
+++ b/server/statistics/hot_cache.go
@@ -16,9 +16,7 @@ package statistics
 
 import (
 	"context"
-	"time"
 
-	"github.com/tikv/pd/pkg/movingaverage"
 	"github.com/tikv/pd/server/core"
 )
 
@@ -190,19 +188,6 @@ func (w *HotCache) ExpiredWriteItems(region *core.RegionInfo) []*HotPeerStat {
 	return w.writeCache.collectExpiredItems(region)
 }
 
-// GetFilledPeriod returns filled period.
-// This is used for mockcluster, for test purpose.
-func (w *HotCache) GetFilledPeriod(kind RWType) int {
-	var reportIntervalSecs int
-	switch kind {
-	case Write:
-		reportIntervalSecs = w.writeCache.kind.ReportInterval()
-	case Read:
-		reportIntervalSecs = w.readCache.kind.ReportInterval()
-	}
-	return movingaverage.NewTimeMedian(DefaultAotSize, rollingWindowsSize, time.Duration(reportIntervalSecs)*time.Second).GetFilledPeriod()
-}
-
 // GetThresholds returns thresholds.
 // This is used for test purpose.
 func (w *HotCache) GetThresholds(kind RWType, storeID uint64) []float64 {