diff --git a/pkg/mock/mockcluster/mockcluster.go b/pkg/mock/mockcluster/mockcluster.go
index d2d51b6e1f5f..6ff059d5fae4 100644
--- a/pkg/mock/mockcluster/mockcluster.go
+++ b/pkg/mock/mockcluster/mockcluster.go
@@ -45,8 +45,6 @@ const (
 	defaultRegionSize    = 96 * units.MiB  // 96MiB
 )
 
-var _ statistics.StoreStatInformer = &Cluster{}
-
 // Cluster is used to mock a cluster for test purpose.
 type Cluster struct {
 	*core.BasicCluster
diff --git a/pkg/movingaverage/exponential_moving_average.go b/pkg/movingaverage/exponential_moving_average.go
index 4e1d1f595658..6c1904a97308 100644
--- a/pkg/movingaverage/exponential_moving_average.go
+++ b/pkg/movingaverage/exponential_moving_average.go
@@ -31,8 +31,6 @@ type EMA struct {
 	instantaneous float64
 }
 
-var _ MovingAvg = &EMA{}
-
 // NewEMA returns an EMA.
 func NewEMA(decays ...float64) *EMA {
 	decay := defaultDecay
diff --git a/pkg/movingaverage/hull_moving_average.go b/pkg/movingaverage/hull_moving_average.go
index 9bb2eda3ea6c..14b550d43f5a 100644
--- a/pkg/movingaverage/hull_moving_average.go
+++ b/pkg/movingaverage/hull_moving_average.go
@@ -26,8 +26,6 @@ type HMA struct {
 	wma  []*WMA
 }
 
-var _ MovingAvg = &HMA{}
-
 // NewHMA returns a WMA.
 func NewHMA(sizes ...float64) *HMA {
 	size := defaultHMASize
diff --git a/pkg/movingaverage/max_filter.go b/pkg/movingaverage/max_filter.go
index 59f9993e7a2c..70bd45f98de5 100644
--- a/pkg/movingaverage/max_filter.go
+++ b/pkg/movingaverage/max_filter.go
@@ -16,8 +16,6 @@ package movingaverage
 
 import "github.com/elliotchance/pie/v2"
 
-var _ MovingAvg = &MaxFilter{}
-
 // MaxFilter works as a maximum filter with specified window size.
 // There are at most `size` data points for calculating.
 type MaxFilter struct {
diff --git a/pkg/movingaverage/moving_average_test.go b/pkg/movingaverage/moving_average_test.go
index 84c235db4846..49c20637c209 100644
--- a/pkg/movingaverage/moving_average_test.go
+++ b/pkg/movingaverage/moving_average_test.go
@@ -80,7 +80,6 @@ func TestMedianFilter(t *testing.T) {
 
 	mf := NewMedianFilter(5)
 	re.Equal(empty, mf.Get())
-	re.Equal([]float64{}, mf.GetAll())
 
 	checkReset(re, mf, empty)
 	checkAdd(re, mf, data, expected)
diff --git a/pkg/movingaverage/weight_moving_average.go b/pkg/movingaverage/weight_moving_average.go
index ce682ec18f35..f8a72b493ee9 100644
--- a/pkg/movingaverage/weight_moving_average.go
+++ b/pkg/movingaverage/weight_moving_average.go
@@ -16,8 +16,6 @@ package movingaverage
 
 const defaultWMASize = 10
 
-var _ MovingAvg = &WMA{}
-
 // WMA works as a weight with specified window size.
 // There are at most `size` data points for calculating.
 // References:https://en.wikipedia.org/wiki/Moving_average#Weighted_moving_average
diff --git a/pkg/statistics/collector.go b/pkg/statistics/collector.go
index 0e93f556fc58..f4785103c890 100644
--- a/pkg/statistics/collector.go
+++ b/pkg/statistics/collector.go
@@ -29,9 +29,6 @@ type storeCollector interface {
 	GetLoads(storeLoads, peerLoadSum []float64, rwTy RWType, kind constant.ResourceKind) (loads []float64)
 }
 
-var _ storeCollector = tikvCollector{}
-var _ storeCollector = tiflashCollector{}
-
 type tikvCollector struct{}
 
 func newTikvCollector() storeCollector {
diff --git a/pkg/statistics/store.go b/pkg/statistics/store.go
index 329a1abb4869..d8288a9b9cf6 100644
--- a/pkg/statistics/store.go
+++ b/pkg/statistics/store.go
@@ -34,8 +34,6 @@ const (
 	RegionsStatsRollingWindowsSize = 9
 )
 
-var _ StoreStatInformer = &StoresStats{}
-
 // StoresStats is a cache hold hot regions.
 type StoresStats struct {
 	syncutil.RWMutex
diff --git a/pkg/statistics/store_hot_peers_infos.go b/pkg/statistics/store_hot_peers_infos.go
index 683977773ab0..ad0f33c9fbe1 100644
--- a/pkg/statistics/store_hot_peers_infos.go
+++ b/pkg/statistics/store_hot_peers_infos.go
@@ -185,8 +185,9 @@ func summaryStoresLoadByEngine(
 		}
 		loads := collector.GetLoads(storeLoads, peerLoadSum, rwTy, kind)
 
+		var historyLoads [][]float64
 		if storesHistoryLoads != nil {
-			historyLoads := storesHistoryLoads.Get(id, rwTy, kind)
+			historyLoads = storesHistoryLoads.Get(id, rwTy, kind)
 			for i, loads := range historyLoads {
 				if allStoreHistoryLoadSum[i] == nil || len(allStoreHistoryLoadSum[i]) < len(loads) {
 					allStoreHistoryLoadSum[i] = make([]float64, len(loads))
diff --git a/pkg/statistics/store_load.go b/pkg/statistics/store_load.go
index 616b39948136..8553f26cde1c 100644
--- a/pkg/statistics/store_load.go
+++ b/pkg/statistics/store_load.go
@@ -15,11 +15,11 @@
 package statistics
 
 import (
-	"github.com/tikv/pd/pkg/core/constant"
 	"math"
 	"time"
 
 	"github.com/tikv/pd/pkg/core"
+	"github.com/tikv/pd/pkg/core/constant"
 )
 
 // StoreLoadDetail records store load information.
@@ -245,10 +245,10 @@ func MaxLoad(a, b *StoreLoad) *StoreLoad {
 }
 
 var (
-	// historyLoadInterval is the duration for saving history load.
-	historyLoadInterval = 30 * time.Second
-	// HistorySampleDuration is the sampling interval for history load
-	HistorySampleDuration = 5 * time.Minute
+	// historySampleInterval is the sampling interval for history load.
+	historySampleInterval = 30 * time.Second
+	// historySampleDuration  is the duration for saving history load.
+	historySampleDuration = 5 * time.Minute
 )
 
 type StoreHistoryLoads struct {
@@ -272,8 +272,8 @@ func (s *StoreHistoryLoads) Add(storeID uint64, rwTp RWType, kind constant.Resou
 	load, ok := s.loads[rwTp][kind][storeID]
 	if !ok {
 		size := 10
-		if historyLoadInterval != 0 {
-			size = int(HistorySampleDuration / historyLoadInterval)
+		if historySampleInterval != 0 {
+			size = int(historySampleDuration / historySampleInterval)
 		}
 		load = newStoreHistoryLoad(size, s.dim)
 		s.loads[rwTp][kind][storeID] = load
@@ -305,7 +305,7 @@ func newStoreHistoryLoad(size int, dim int) *storeHistoryLoad {
 }
 
 func (s *storeHistoryLoad) add(loads []float64) {
-	if time.Now().Sub(s.update) < historyLoadInterval {
+	if time.Now().Sub(s.update) < historySampleInterval {
 		return
 	}
 	if s.count == 0 {
diff --git a/pkg/statistics/store_load_test.go b/pkg/statistics/store_load_test.go
index ff69d99447cd..ea4246edec64 100644
--- a/pkg/statistics/store_load_test.go
+++ b/pkg/statistics/store_load_test.go
@@ -23,7 +23,7 @@ import (
 
 func TestHistoryLoads(t *testing.T) {
 	re := require.New(t)
-	historyLoadInterval = 0
+	historySampleInterval = 0
 	historyLoads := NewStoreHistoryLoads(DimLen)
 	loads := []float64{1.0, 2.0, 3.0}
 	rwTp := Read
diff --git a/server/cluster/cluster.go b/server/cluster/cluster.go
index 8fa3f5bfea22..c4b9db33ea5f 100644
--- a/server/cluster/cluster.go
+++ b/server/cluster/cluster.go
@@ -109,8 +109,6 @@ type Server interface {
 	ReplicateFileToMember(ctx context.Context, member *pdpb.Member, name string, data []byte) error
 }
 
-var _ statistics.StoreStatInformer = &RaftCluster{}
-
 // RaftCluster is used for cluster config management.
 // Raft cluster key format:
 // cluster 1 -> /1/raft, value is metapb.Cluster
diff --git a/server/handler.go b/server/handler.go
index c752403f3265..35cec65527f9 100644
--- a/server/handler.go
+++ b/server/handler.go
@@ -78,8 +78,6 @@ var (
 	schedulerConfigPrefix = "pd/api/v1/scheduler-config"
 )
 
-var _ statistics.StoreStatInformer = &Handler{}
-
 // Handler is a helper to export methods to handle API/RPC requests.
 type Handler struct {
 	s               *Server