diff --git a/aggregationpb/aggregation.pb.go b/aggregationpb/aggregation.pb.go
index fc001ac..0a74387 100644
--- a/aggregationpb/aggregation.pb.go
+++ b/aggregationpb/aggregation.pb.go
@@ -1193,17 +1193,21 @@ func (x *SpanMetrics) GetSum() float64 {
 	return 0
 }
 
-type CountValue struct {
+type Overflow struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
 	unknownFields protoimpl.UnknownFields
 
-	Count int64 `protobuf:"varint,1,opt,name=count,proto3" json:"count,omitempty"`
-	Value int64 `protobuf:"varint,2,opt,name=value,proto3" json:"value,omitempty"`
+	OverflowTransactions                 *TransactionMetrics        `protobuf:"bytes,1,opt,name=overflow_transactions,json=overflowTransactions,proto3" json:"overflow_transactions,omitempty"`
+	OverflowServiceTransactions          *ServiceTransactionMetrics `protobuf:"bytes,2,opt,name=overflow_service_transactions,json=overflowServiceTransactions,proto3" json:"overflow_service_transactions,omitempty"`
+	OverflowSpans                        *SpanMetrics               `protobuf:"bytes,3,opt,name=overflow_spans,json=overflowSpans,proto3" json:"overflow_spans,omitempty"`
+	OverflowTransactionsEstimator        []byte                     `protobuf:"bytes,4,opt,name=overflow_transactions_estimator,json=overflowTransactionsEstimator,proto3" json:"overflow_transactions_estimator,omitempty"`
+	OverflowServiceTransactionsEstimator []byte                     `protobuf:"bytes,5,opt,name=overflow_service_transactions_estimator,json=overflowServiceTransactionsEstimator,proto3" json:"overflow_service_transactions_estimator,omitempty"`
+	OverflowSpansEstimator               []byte                     `protobuf:"bytes,6,opt,name=overflow_spans_estimator,json=overflowSpansEstimator,proto3" json:"overflow_spans_estimator,omitempty"`
 }
 
-func (x *CountValue) Reset() {
-	*x = CountValue{}
+func (x *Overflow) Reset() {
+	*x = Overflow{}
 	if protoimpl.UnsafeEnabled {
 		mi := &file_proto_aggregation_proto_msgTypes[16]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
@@ -1211,13 +1215,13 @@ func (x *CountValue) Reset() {
 	}
 }
 
-func (x *CountValue) String() string {
+func (x *Overflow) String() string {
 	return protoimpl.X.MessageStringOf(x)
 }
 
-func (*CountValue) ProtoMessage() {}
+func (*Overflow) ProtoMessage() {}
 
-func (x *CountValue) ProtoReflect() protoreflect.Message {
+func (x *Overflow) ProtoReflect() protoreflect.Message {
 	mi := &file_proto_aggregation_proto_msgTypes[16]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
@@ -1229,23 +1233,51 @@ func (x *CountValue) ProtoReflect() protoreflect.Message {
 	return mi.MessageOf(x)
 }
 
-// Deprecated: Use CountValue.ProtoReflect.Descriptor instead.
-func (*CountValue) Descriptor() ([]byte, []int) {
+// Deprecated: Use Overflow.ProtoReflect.Descriptor instead.
+func (*Overflow) Descriptor() ([]byte, []int) {
 	return file_proto_aggregation_proto_rawDescGZIP(), []int{16}
 }
 
-func (x *CountValue) GetCount() int64 {
+func (x *Overflow) GetOverflowTransactions() *TransactionMetrics {
 	if x != nil {
-		return x.Count
+		return x.OverflowTransactions
 	}
-	return 0
+	return nil
 }
 
-func (x *CountValue) GetValue() int64 {
+func (x *Overflow) GetOverflowServiceTransactions() *ServiceTransactionMetrics {
 	if x != nil {
-		return x.Value
+		return x.OverflowServiceTransactions
 	}
-	return 0
+	return nil
+}
+
+func (x *Overflow) GetOverflowSpans() *SpanMetrics {
+	if x != nil {
+		return x.OverflowSpans
+	}
+	return nil
+}
+
+func (x *Overflow) GetOverflowTransactionsEstimator() []byte {
+	if x != nil {
+		return x.OverflowTransactionsEstimator
+	}
+	return nil
+}
+
+func (x *Overflow) GetOverflowServiceTransactionsEstimator() []byte {
+	if x != nil {
+		return x.OverflowServiceTransactionsEstimator
+	}
+	return nil
+}
+
+func (x *Overflow) GetOverflowSpansEstimator() []byte {
+	if x != nil {
+		return x.OverflowSpansEstimator
+	}
+	return nil
 }
 
 type HDRHistogram struct {
@@ -1327,93 +1359,6 @@ func (x *HDRHistogram) GetBuckets() []int32 {
 	return nil
 }
 
-type Overflow struct {
-	state         protoimpl.MessageState
-	sizeCache     protoimpl.SizeCache
-	unknownFields protoimpl.UnknownFields
-
-	OverflowTransactions                 *TransactionMetrics        `protobuf:"bytes,1,opt,name=overflow_transactions,json=overflowTransactions,proto3" json:"overflow_transactions,omitempty"`
-	OverflowServiceTransactions          *ServiceTransactionMetrics `protobuf:"bytes,2,opt,name=overflow_service_transactions,json=overflowServiceTransactions,proto3" json:"overflow_service_transactions,omitempty"`
-	OverflowSpans                        *SpanMetrics               `protobuf:"bytes,3,opt,name=overflow_spans,json=overflowSpans,proto3" json:"overflow_spans,omitempty"`
-	OverflowTransactionsEstimator        []byte                     `protobuf:"bytes,4,opt,name=overflow_transactions_estimator,json=overflowTransactionsEstimator,proto3" json:"overflow_transactions_estimator,omitempty"`
-	OverflowServiceTransactionsEstimator []byte                     `protobuf:"bytes,5,opt,name=overflow_service_transactions_estimator,json=overflowServiceTransactionsEstimator,proto3" json:"overflow_service_transactions_estimator,omitempty"`
-	OverflowSpansEstimator               []byte                     `protobuf:"bytes,6,opt,name=overflow_spans_estimator,json=overflowSpansEstimator,proto3" json:"overflow_spans_estimator,omitempty"`
-}
-
-func (x *Overflow) Reset() {
-	*x = Overflow{}
-	if protoimpl.UnsafeEnabled {
-		mi := &file_proto_aggregation_proto_msgTypes[18]
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		ms.StoreMessageInfo(mi)
-	}
-}
-
-func (x *Overflow) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*Overflow) ProtoMessage() {}
-
-func (x *Overflow) ProtoReflect() protoreflect.Message {
-	mi := &file_proto_aggregation_proto_msgTypes[18]
-	if protoimpl.UnsafeEnabled && x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use Overflow.ProtoReflect.Descriptor instead.
-func (*Overflow) Descriptor() ([]byte, []int) {
-	return file_proto_aggregation_proto_rawDescGZIP(), []int{18}
-}
-
-func (x *Overflow) GetOverflowTransactions() *TransactionMetrics {
-	if x != nil {
-		return x.OverflowTransactions
-	}
-	return nil
-}
-
-func (x *Overflow) GetOverflowServiceTransactions() *ServiceTransactionMetrics {
-	if x != nil {
-		return x.OverflowServiceTransactions
-	}
-	return nil
-}
-
-func (x *Overflow) GetOverflowSpans() *SpanMetrics {
-	if x != nil {
-		return x.OverflowSpans
-	}
-	return nil
-}
-
-func (x *Overflow) GetOverflowTransactionsEstimator() []byte {
-	if x != nil {
-		return x.OverflowTransactionsEstimator
-	}
-	return nil
-}
-
-func (x *Overflow) GetOverflowServiceTransactionsEstimator() []byte {
-	if x != nil {
-		return x.OverflowServiceTransactionsEstimator
-	}
-	return nil
-}
-
-func (x *Overflow) GetOverflowSpansEstimator() []byte {
-	if x != nil {
-		return x.OverflowSpansEstimator
-	}
-	return nil
-}
-
 var File_proto_aggregation_proto protoreflect.FileDescriptor
 
 var file_proto_aggregation_proto_rawDesc = []byte{
@@ -1648,57 +1593,53 @@ var file_proto_aggregation_proto_rawDesc = []byte{
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+	0x65, 0x18, 0x02, 0x20, 0x01, 0x28, 0x03, 0x52, 0x15, 0x68, 0x69, 0x67, 0x68, 0x65, 0x73, 0x74,
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+	0x67, 0x75, 0x72, 0x65, 0x73, 0x18, 0x03, 0x20, 0x01, 0x28, 0x03, 0x52, 0x12, 0x73, 0x69, 0x67,
+	0x6e, 0x69, 0x66, 0x69, 0x63, 0x61, 0x6e, 0x74, 0x46, 0x69, 0x67, 0x75, 0x72, 0x65, 0x73, 0x12,
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+	0x06, 0x63, 0x6f, 0x75, 0x6e, 0x74, 0x73, 0x12, 0x18, 0x0a, 0x07, 0x62, 0x75, 0x63, 0x6b, 0x65,
+	0x74, 0x73, 0x18, 0x05, 0x20, 0x03, 0x28, 0x05, 0x52, 0x07, 0x62, 0x75, 0x63, 0x6b, 0x65, 0x74,
+	0x73, 0x42, 0x13, 0x48, 0x01, 0x5a, 0x0f, 0x2e, 0x2f, 0x61, 0x67, 0x67, 0x72, 0x65, 0x67, 0x61,
+	0x74, 0x69, 0x6f, 0x6e, 0x70, 0x62, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (
@@ -1713,7 +1654,7 @@ func file_proto_aggregation_proto_rawDescGZIP() []byte {
 	return file_proto_aggregation_proto_rawDescData
 }
 
-var file_proto_aggregation_proto_msgTypes = make([]protoimpl.MessageInfo, 19)
+var file_proto_aggregation_proto_msgTypes = make([]protoimpl.MessageInfo, 18)
 var file_proto_aggregation_proto_goTypes = []interface{}{
 	(*CombinedMetrics)(nil),                  // 0: elastic.apm.CombinedMetrics
 	(*KeyedServiceMetrics)(nil),              // 1: elastic.apm.KeyedServiceMetrics
@@ -1731,17 +1672,16 @@ var file_proto_aggregation_proto_goTypes = []interface{}{
 	(*KeyedSpanMetrics)(nil),                 // 13: elastic.apm.KeyedSpanMetrics
 	(*SpanAggregationKey)(nil),               // 14: elastic.apm.SpanAggregationKey
 	(*SpanMetrics)(nil),                      // 15: elastic.apm.SpanMetrics
-	(*CountValue)(nil),                       // 16: elastic.apm.CountValue
+	(*Overflow)(nil),                         // 16: elastic.apm.Overflow
 	(*HDRHistogram)(nil),                     // 17: elastic.apm.HDRHistogram
-	(*Overflow)(nil),                         // 18: elastic.apm.Overflow
 }
 var file_proto_aggregation_proto_depIdxs = []int32{
 	1,  // 0: elastic.apm.CombinedMetrics.service_metrics:type_name -> elastic.apm.KeyedServiceMetrics
-	18, // 1: elastic.apm.CombinedMetrics.overflow_services:type_name -> elastic.apm.Overflow
+	16, // 1: elastic.apm.CombinedMetrics.overflow_services:type_name -> elastic.apm.Overflow
 	2,  // 2: elastic.apm.KeyedServiceMetrics.key:type_name -> elastic.apm.ServiceAggregationKey
 	3,  // 3: elastic.apm.KeyedServiceMetrics.metrics:type_name -> elastic.apm.ServiceMetrics
 	6,  // 4: elastic.apm.ServiceMetrics.service_instance_metrics:type_name -> elastic.apm.KeyedServiceInstanceMetrics
-	18, // 5: elastic.apm.ServiceMetrics.overflow_groups:type_name -> elastic.apm.Overflow
+	16, // 5: elastic.apm.ServiceMetrics.overflow_groups:type_name -> elastic.apm.Overflow
 	7,  // 6: elastic.apm.ServiceInstanceMetrics.transaction_metrics:type_name -> elastic.apm.KeyedTransactionMetrics
 	10, // 7: elastic.apm.ServiceInstanceMetrics.service_transaction_metrics:type_name -> elastic.apm.KeyedServiceTransactionMetrics
 	13, // 8: elastic.apm.ServiceInstanceMetrics.span_metrics:type_name -> elastic.apm.KeyedSpanMetrics
@@ -1964,7 +1904,7 @@ func file_proto_aggregation_proto_init() {
 			}
 		}
 		file_proto_aggregation_proto_msgTypes[16].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*CountValue); i {
+			switch v := v.(*Overflow); i {
 			case 0:
 				return &v.state
 			case 1:
@@ -1987,18 +1927,6 @@ func file_proto_aggregation_proto_init() {
 				return nil
 			}
 		}
-		file_proto_aggregation_proto_msgTypes[18].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*Overflow); i {
-			case 0:
-				return &v.state
-			case 1:
-				return &v.sizeCache
-			case 2:
-				return &v.unknownFields
-			default:
-				return nil
-			}
-		}
 	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
@@ -2006,7 +1934,7 @@ func file_proto_aggregation_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: file_proto_aggregation_proto_rawDesc,
 			NumEnums:      0,
-			NumMessages:   19,
+			NumMessages:   18,
 			NumExtensions: 0,
 			NumServices:   0,
 		},
diff --git a/aggregationpb/aggregation_vtproto.pb.go b/aggregationpb/aggregation_vtproto.pb.go
index c93f8dc..70c8565 100644
--- a/aggregationpb/aggregation_vtproto.pb.go
+++ b/aggregationpb/aggregation_vtproto.pb.go
@@ -407,13 +407,29 @@ func (m *SpanMetrics) CloneMessageVT() proto.Message {
 	return m.CloneVT()
 }
 
-func (m *CountValue) CloneVT() *CountValue {
+func (m *Overflow) CloneVT() *Overflow {
 	if m == nil {
-		return (*CountValue)(nil)
+		return (*Overflow)(nil)
 	}
-	r := &CountValue{
-		Count: m.Count,
-		Value: m.Value,
+	r := &Overflow{
+		OverflowTransactions:        m.OverflowTransactions.CloneVT(),
+		OverflowServiceTransactions: m.OverflowServiceTransactions.CloneVT(),
+		OverflowSpans:               m.OverflowSpans.CloneVT(),
+	}
+	if rhs := m.OverflowTransactionsEstimator; rhs != nil {
+		tmpBytes := make([]byte, len(rhs))
+		copy(tmpBytes, rhs)
+		r.OverflowTransactionsEstimator = tmpBytes
+	}
+	if rhs := m.OverflowServiceTransactionsEstimator; rhs != nil {
+		tmpBytes := make([]byte, len(rhs))
+		copy(tmpBytes, rhs)
+		r.OverflowServiceTransactionsEstimator = tmpBytes
+	}
+	if rhs := m.OverflowSpansEstimator; rhs != nil {
+		tmpBytes := make([]byte, len(rhs))
+		copy(tmpBytes, rhs)
+		r.OverflowSpansEstimator = tmpBytes
 	}
 	if len(m.unknownFields) > 0 {
 		r.unknownFields = make([]byte, len(m.unknownFields))
@@ -422,7 +438,7 @@ func (m *CountValue) CloneVT() *CountValue {
 	return r
 }
 
-func (m *CountValue) CloneMessageVT() proto.Message {
+func (m *Overflow) CloneMessageVT() proto.Message {
 	return m.CloneVT()
 }
 
@@ -456,41 +472,6 @@ func (m *HDRHistogram) CloneMessageVT() proto.Message {
 	return m.CloneVT()
 }
 
-func (m *Overflow) CloneVT() *Overflow {
-	if m == nil {
-		return (*Overflow)(nil)
-	}
-	r := &Overflow{
-		OverflowTransactions:        m.OverflowTransactions.CloneVT(),
-		OverflowServiceTransactions: m.OverflowServiceTransactions.CloneVT(),
-		OverflowSpans:               m.OverflowSpans.CloneVT(),
-	}
-	if rhs := m.OverflowTransactionsEstimator; rhs != nil {
-		tmpBytes := make([]byte, len(rhs))
-		copy(tmpBytes, rhs)
-		r.OverflowTransactionsEstimator = tmpBytes
-	}
-	if rhs := m.OverflowServiceTransactionsEstimator; rhs != nil {
-		tmpBytes := make([]byte, len(rhs))
-		copy(tmpBytes, rhs)
-		r.OverflowServiceTransactionsEstimator = tmpBytes
-	}
-	if rhs := m.OverflowSpansEstimator; rhs != nil {
-		tmpBytes := make([]byte, len(rhs))
-		copy(tmpBytes, rhs)
-		r.OverflowSpansEstimator = tmpBytes
-	}
-	if len(m.unknownFields) > 0 {
-		r.unknownFields = make([]byte, len(m.unknownFields))
-		copy(r.unknownFields, m.unknownFields)
-	}
-	return r
-}
-
-func (m *Overflow) CloneMessageVT() proto.Message {
-	return m.CloneVT()
-}
-
 func (m *CombinedMetrics) MarshalVT() (dAtA []byte, err error) {
 	if m == nil {
 		return nil, nil
@@ -1582,7 +1563,7 @@ func (m *SpanMetrics) MarshalToSizedBufferVT(dAtA []byte) (int, error) {
 	return len(dAtA) - i, nil
 }
 
-func (m *CountValue) MarshalVT() (dAtA []byte, err error) {
+func (m *Overflow) MarshalVT() (dAtA []byte, err error) {
 	if m == nil {
 		return nil, nil
 	}
@@ -1595,12 +1576,12 @@ func (m *CountValue) MarshalVT() (dAtA []byte, err error) {
 	return dAtA[:n], nil
 }
 
-func (m *CountValue) MarshalToVT(dAtA []byte) (int, error) {
+func (m *Overflow) MarshalToVT(dAtA []byte) (int, error) {
 	size := m.SizeVT()
 	return m.MarshalToSizedBufferVT(dAtA[:size])
 }
 
-func (m *CountValue) MarshalToSizedBufferVT(dAtA []byte) (int, error) {
+func (m *Overflow) MarshalToSizedBufferVT(dAtA []byte) (int, error) {
 	if m == nil {
 		return 0, nil
 	}
@@ -1612,15 +1593,56 @@ func (m *CountValue) MarshalToSizedBufferVT(dAtA []byte) (int, error) {
 		i -= len(m.unknownFields)
 		copy(dAtA[i:], m.unknownFields)
 	}
-	if m.Value != 0 {
-		i = encodeVarint(dAtA, i, uint64(m.Value))
+	if len(m.OverflowSpansEstimator) > 0 {
+		i -= len(m.OverflowSpansEstimator)
+		copy(dAtA[i:], m.OverflowSpansEstimator)
+		i = encodeVarint(dAtA, i, uint64(len(m.OverflowSpansEstimator)))
+		i--
+		dAtA[i] = 0x32
+	}
+	if len(m.OverflowServiceTransactionsEstimator) > 0 {
+		i -= len(m.OverflowServiceTransactionsEstimator)
+		copy(dAtA[i:], m.OverflowServiceTransactionsEstimator)
+		i = encodeVarint(dAtA, i, uint64(len(m.OverflowServiceTransactionsEstimator)))
 		i--
-		dAtA[i] = 0x10
+		dAtA[i] = 0x2a
 	}
-	if m.Count != 0 {
-		i = encodeVarint(dAtA, i, uint64(m.Count))
+	if len(m.OverflowTransactionsEstimator) > 0 {
+		i -= len(m.OverflowTransactionsEstimator)
+		copy(dAtA[i:], m.OverflowTransactionsEstimator)
+		i = encodeVarint(dAtA, i, uint64(len(m.OverflowTransactionsEstimator)))
 		i--
-		dAtA[i] = 0x8
+		dAtA[i] = 0x22
+	}
+	if m.OverflowSpans != nil {
+		size, err := m.OverflowSpans.MarshalToSizedBufferVT(dAtA[:i])
+		if err != nil {
+			return 0, err
+		}
+		i -= size
+		i = encodeVarint(dAtA, i, uint64(size))
+		i--
+		dAtA[i] = 0x1a
+	}
+	if m.OverflowServiceTransactions != nil {
+		size, err := m.OverflowServiceTransactions.MarshalToSizedBufferVT(dAtA[:i])
+		if err != nil {
+			return 0, err
+		}
+		i -= size
+		i = encodeVarint(dAtA, i, uint64(size))
+		i--
+		dAtA[i] = 0x12
+	}
+	if m.OverflowTransactions != nil {
+		size, err := m.OverflowTransactions.MarshalToSizedBufferVT(dAtA[:i])
+		if err != nil {
+			return 0, err
+		}
+		i -= size
+		i = encodeVarint(dAtA, i, uint64(size))
+		i--
+		dAtA[i] = 0xa
 	}
 	return len(dAtA) - i, nil
 }
@@ -1715,90 +1737,6 @@ func (m *HDRHistogram) MarshalToSizedBufferVT(dAtA []byte) (int, error) {
 	return len(dAtA) - i, nil
 }
 
-func (m *Overflow) MarshalVT() (dAtA []byte, err error) {
-	if m == nil {
-		return nil, nil
-	}
-	size := m.SizeVT()
-	dAtA = make([]byte, size)
-	n, err := m.MarshalToSizedBufferVT(dAtA[:size])
-	if err != nil {
-		return nil, err
-	}
-	return dAtA[:n], nil
-}
-
-func (m *Overflow) MarshalToVT(dAtA []byte) (int, error) {
-	size := m.SizeVT()
-	return m.MarshalToSizedBufferVT(dAtA[:size])
-}
-
-func (m *Overflow) MarshalToSizedBufferVT(dAtA []byte) (int, error) {
-	if m == nil {
-		return 0, nil
-	}
-	i := len(dAtA)
-	_ = i
-	var l int
-	_ = l
-	if m.unknownFields != nil {
-		i -= len(m.unknownFields)
-		copy(dAtA[i:], m.unknownFields)
-	}
-	if len(m.OverflowSpansEstimator) > 0 {
-		i -= len(m.OverflowSpansEstimator)
-		copy(dAtA[i:], m.OverflowSpansEstimator)
-		i = encodeVarint(dAtA, i, uint64(len(m.OverflowSpansEstimator)))
-		i--
-		dAtA[i] = 0x32
-	}
-	if len(m.OverflowServiceTransactionsEstimator) > 0 {
-		i -= len(m.OverflowServiceTransactionsEstimator)
-		copy(dAtA[i:], m.OverflowServiceTransactionsEstimator)
-		i = encodeVarint(dAtA, i, uint64(len(m.OverflowServiceTransactionsEstimator)))
-		i--
-		dAtA[i] = 0x2a
-	}
-	if len(m.OverflowTransactionsEstimator) > 0 {
-		i -= len(m.OverflowTransactionsEstimator)
-		copy(dAtA[i:], m.OverflowTransactionsEstimator)
-		i = encodeVarint(dAtA, i, uint64(len(m.OverflowTransactionsEstimator)))
-		i--
-		dAtA[i] = 0x22
-	}
-	if m.OverflowSpans != nil {
-		size, err := m.OverflowSpans.MarshalToSizedBufferVT(dAtA[:i])
-		if err != nil {
-			return 0, err
-		}
-		i -= size
-		i = encodeVarint(dAtA, i, uint64(size))
-		i--
-		dAtA[i] = 0x1a
-	}
-	if m.OverflowServiceTransactions != nil {
-		size, err := m.OverflowServiceTransactions.MarshalToSizedBufferVT(dAtA[:i])
-		if err != nil {
-			return 0, err
-		}
-		i -= size
-		i = encodeVarint(dAtA, i, uint64(size))
-		i--
-		dAtA[i] = 0x12
-	}
-	if m.OverflowTransactions != nil {
-		size, err := m.OverflowTransactions.MarshalToSizedBufferVT(dAtA[:i])
-		if err != nil {
-			return 0, err
-		}
-		i -= size
-		i = encodeVarint(dAtA, i, uint64(size))
-		i--
-		dAtA[i] = 0xa
-	}
-	return len(dAtA) - i, nil
-}
-
 func encodeVarint(dAtA []byte, offset int, v uint64) int {
 	offset -= sov(v)
 	base := offset
@@ -2165,23 +2103,32 @@ func SpanMetricsFromVTPool() *SpanMetrics {
 	return vtprotoPool_SpanMetrics.Get().(*SpanMetrics)
 }
 
-var vtprotoPool_CountValue = sync.Pool{
+var vtprotoPool_Overflow = sync.Pool{
 	New: func() interface{} {
-		return &CountValue{}
+		return &Overflow{}
 	},
 }
 
-func (m *CountValue) ResetVT() {
+func (m *Overflow) ResetVT() {
+	m.OverflowTransactions.ReturnToVTPool()
+	m.OverflowServiceTransactions.ReturnToVTPool()
+	m.OverflowSpans.ReturnToVTPool()
+	f0 := m.OverflowTransactionsEstimator[:0]
+	f1 := m.OverflowServiceTransactionsEstimator[:0]
+	f2 := m.OverflowSpansEstimator[:0]
 	m.Reset()
+	m.OverflowTransactionsEstimator = f0
+	m.OverflowServiceTransactionsEstimator = f1
+	m.OverflowSpansEstimator = f2
 }
-func (m *CountValue) ReturnToVTPool() {
+func (m *Overflow) ReturnToVTPool() {
 	if m != nil {
 		m.ResetVT()
-		vtprotoPool_CountValue.Put(m)
+		vtprotoPool_Overflow.Put(m)
 	}
 }
-func CountValueFromVTPool() *CountValue {
-	return vtprotoPool_CountValue.Get().(*CountValue)
+func OverflowFromVTPool() *Overflow {
+	return vtprotoPool_Overflow.Get().(*Overflow)
 }
 
 var vtprotoPool_HDRHistogram = sync.Pool{
@@ -2206,34 +2153,6 @@ func (m *HDRHistogram) ReturnToVTPool() {
 func HDRHistogramFromVTPool() *HDRHistogram {
 	return vtprotoPool_HDRHistogram.Get().(*HDRHistogram)
 }
-
-var vtprotoPool_Overflow = sync.Pool{
-	New: func() interface{} {
-		return &Overflow{}
-	},
-}
-
-func (m *Overflow) ResetVT() {
-	m.OverflowTransactions.ReturnToVTPool()
-	m.OverflowServiceTransactions.ReturnToVTPool()
-	m.OverflowSpans.ReturnToVTPool()
-	f0 := m.OverflowTransactionsEstimator[:0]
-	f1 := m.OverflowServiceTransactionsEstimator[:0]
-	f2 := m.OverflowSpansEstimator[:0]
-	m.Reset()
-	m.OverflowTransactionsEstimator = f0
-	m.OverflowServiceTransactionsEstimator = f1
-	m.OverflowSpansEstimator = f2
-}
-func (m *Overflow) ReturnToVTPool() {
-	if m != nil {
-		m.ResetVT()
-		vtprotoPool_Overflow.Put(m)
-	}
-}
-func OverflowFromVTPool() *Overflow {
-	return vtprotoPool_Overflow.Get().(*Overflow)
-}
 func (m *CombinedMetrics) SizeVT() (n int) {
 	if m == nil {
 		return 0
@@ -2667,27 +2586,45 @@ func (m *SpanMetrics) SizeVT() (n int) {
 	return n
 }
 
-func (m *CountValue) SizeVT() (n int) {
+func (m *Overflow) SizeVT() (n int) {
 	if m == nil {
 		return 0
 	}
 	var l int
 	_ = l
-	if m.Count != 0 {
-		n += 1 + sov(uint64(m.Count))
-	}
-	if m.Value != 0 {
-		n += 1 + sov(uint64(m.Value))
+	if m.OverflowTransactions != nil {
+		l = m.OverflowTransactions.SizeVT()
+		n += 1 + l + sov(uint64(l))
 	}
-	n += len(m.unknownFields)
-	return n
-}
-
-func (m *HDRHistogram) SizeVT() (n int) {
-	if m == nil {
-		return 0
+	if m.OverflowServiceTransactions != nil {
+		l = m.OverflowServiceTransactions.SizeVT()
+		n += 1 + l + sov(uint64(l))
 	}
-	var l int
+	if m.OverflowSpans != nil {
+		l = m.OverflowSpans.SizeVT()
+		n += 1 + l + sov(uint64(l))
+	}
+	l = len(m.OverflowTransactionsEstimator)
+	if l > 0 {
+		n += 1 + l + sov(uint64(l))
+	}
+	l = len(m.OverflowServiceTransactionsEstimator)
+	if l > 0 {
+		n += 1 + l + sov(uint64(l))
+	}
+	l = len(m.OverflowSpansEstimator)
+	if l > 0 {
+		n += 1 + l + sov(uint64(l))
+	}
+	n += len(m.unknownFields)
+	return n
+}
+
+func (m *HDRHistogram) SizeVT() (n int) {
+	if m == nil {
+		return 0
+	}
+	var l int
 	_ = l
 	if m.LowestTrackableValue != 0 {
 		n += 1 + sov(uint64(m.LowestTrackableValue))
@@ -2716,40 +2653,6 @@ func (m *HDRHistogram) SizeVT() (n int) {
 	return n
 }
 
-func (m *Overflow) SizeVT() (n int) {
-	if m == nil {
-		return 0
-	}
-	var l int
-	_ = l
-	if m.OverflowTransactions != nil {
-		l = m.OverflowTransactions.SizeVT()
-		n += 1 + l + sov(uint64(l))
-	}
-	if m.OverflowServiceTransactions != nil {
-		l = m.OverflowServiceTransactions.SizeVT()
-		n += 1 + l + sov(uint64(l))
-	}
-	if m.OverflowSpans != nil {
-		l = m.OverflowSpans.SizeVT()
-		n += 1 + l + sov(uint64(l))
-	}
-	l = len(m.OverflowTransactionsEstimator)
-	if l > 0 {
-		n += 1 + l + sov(uint64(l))
-	}
-	l = len(m.OverflowServiceTransactionsEstimator)
-	if l > 0 {
-		n += 1 + l + sov(uint64(l))
-	}
-	l = len(m.OverflowSpansEstimator)
-	if l > 0 {
-		n += 1 + l + sov(uint64(l))
-	}
-	n += len(m.unknownFields)
-	return n
-}
-
 func sov(x uint64) (n int) {
 	return (bits.Len64(x|1) + 6) / 7
 }
@@ -5699,7 +5602,7 @@ func (m *SpanMetrics) UnmarshalVT(dAtA []byte) error {
 	}
 	return nil
 }
-func (m *CountValue) UnmarshalVT(dAtA []byte) error {
+func (m *Overflow) UnmarshalVT(dAtA []byte) error {
 	l := len(dAtA)
 	iNdEx := 0
 	for iNdEx < l {
@@ -5722,17 +5625,17 @@ func (m *CountValue) UnmarshalVT(dAtA []byte) error {
 		fieldNum := int32(wire >> 3)
 		wireType := int(wire & 0x7)
 		if wireType == 4 {
-			return fmt.Errorf("proto: CountValue: wiretype end group for non-group")
+			return fmt.Errorf("proto: Overflow: wiretype end group for non-group")
 		}
 		if fieldNum <= 0 {
-			return fmt.Errorf("proto: CountValue: illegal tag %d (wire type %d)", fieldNum, wire)
+			return fmt.Errorf("proto: Overflow: illegal tag %d (wire type %d)", fieldNum, wire)
 		}
 		switch fieldNum {
 		case 1:
-			if wireType != 0 {
-				return fmt.Errorf("proto: wrong wireType = %d for field Count", wireType)
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field OverflowTransactions", wireType)
 			}
-			m.Count = 0
+			var msglen int
 			for shift := uint(0); ; shift += 7 {
 				if shift >= 64 {
 					return ErrIntOverflow
@@ -5742,16 +5645,33 @@ func (m *CountValue) UnmarshalVT(dAtA []byte) error {
 				}
 				b := dAtA[iNdEx]
 				iNdEx++
-				m.Count |= int64(b&0x7F) << shift
+				msglen |= int(b&0x7F) << shift
 				if b < 0x80 {
 					break
 				}
 			}
+			if msglen < 0 {
+				return ErrInvalidLength
+			}
+			postIndex := iNdEx + msglen
+			if postIndex < 0 {
+				return ErrInvalidLength
+			}
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			if m.OverflowTransactions == nil {
+				m.OverflowTransactions = TransactionMetricsFromVTPool()
+			}
+			if err := m.OverflowTransactions.UnmarshalVT(dAtA[iNdEx:postIndex]); err != nil {
+				return err
+			}
+			iNdEx = postIndex
 		case 2:
-			if wireType != 0 {
-				return fmt.Errorf("proto: wrong wireType = %d for field Value", wireType)
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field OverflowServiceTransactions", wireType)
 			}
-			m.Value = 0
+			var msglen int
 			for shift := uint(0); ; shift += 7 {
 				if shift >= 64 {
 					return ErrIntOverflow
@@ -5761,11 +5681,166 @@ func (m *CountValue) UnmarshalVT(dAtA []byte) error {
 				}
 				b := dAtA[iNdEx]
 				iNdEx++
-				m.Value |= int64(b&0x7F) << shift
+				msglen |= int(b&0x7F) << shift
 				if b < 0x80 {
 					break
 				}
 			}
+			if msglen < 0 {
+				return ErrInvalidLength
+			}
+			postIndex := iNdEx + msglen
+			if postIndex < 0 {
+				return ErrInvalidLength
+			}
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			if m.OverflowServiceTransactions == nil {
+				m.OverflowServiceTransactions = ServiceTransactionMetricsFromVTPool()
+			}
+			if err := m.OverflowServiceTransactions.UnmarshalVT(dAtA[iNdEx:postIndex]); err != nil {
+				return err
+			}
+			iNdEx = postIndex
+		case 3:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field OverflowSpans", wireType)
+			}
+			var msglen int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflow
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				msglen |= int(b&0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			if msglen < 0 {
+				return ErrInvalidLength
+			}
+			postIndex := iNdEx + msglen
+			if postIndex < 0 {
+				return ErrInvalidLength
+			}
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			if m.OverflowSpans == nil {
+				m.OverflowSpans = SpanMetricsFromVTPool()
+			}
+			if err := m.OverflowSpans.UnmarshalVT(dAtA[iNdEx:postIndex]); err != nil {
+				return err
+			}
+			iNdEx = postIndex
+		case 4:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field OverflowTransactionsEstimator", wireType)
+			}
+			var byteLen int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflow
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				byteLen |= int(b&0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			if byteLen < 0 {
+				return ErrInvalidLength
+			}
+			postIndex := iNdEx + byteLen
+			if postIndex < 0 {
+				return ErrInvalidLength
+			}
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.OverflowTransactionsEstimator = append(m.OverflowTransactionsEstimator[:0], dAtA[iNdEx:postIndex]...)
+			if m.OverflowTransactionsEstimator == nil {
+				m.OverflowTransactionsEstimator = []byte{}
+			}
+			iNdEx = postIndex
+		case 5:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field OverflowServiceTransactionsEstimator", wireType)
+			}
+			var byteLen int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflow
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				byteLen |= int(b&0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			if byteLen < 0 {
+				return ErrInvalidLength
+			}
+			postIndex := iNdEx + byteLen
+			if postIndex < 0 {
+				return ErrInvalidLength
+			}
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.OverflowServiceTransactionsEstimator = append(m.OverflowServiceTransactionsEstimator[:0], dAtA[iNdEx:postIndex]...)
+			if m.OverflowServiceTransactionsEstimator == nil {
+				m.OverflowServiceTransactionsEstimator = []byte{}
+			}
+			iNdEx = postIndex
+		case 6:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field OverflowSpansEstimator", wireType)
+			}
+			var byteLen int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflow
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				byteLen |= int(b&0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			if byteLen < 0 {
+				return ErrInvalidLength
+			}
+			postIndex := iNdEx + byteLen
+			if postIndex < 0 {
+				return ErrInvalidLength
+			}
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			m.OverflowSpansEstimator = append(m.OverflowSpansEstimator[:0], dAtA[iNdEx:postIndex]...)
+			if m.OverflowSpansEstimator == nil {
+				m.OverflowSpansEstimator = []byte{}
+			}
+			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
 			skippy, err := skip(dAtA[iNdEx:])
@@ -6048,267 +6123,6 @@ func (m *HDRHistogram) UnmarshalVT(dAtA []byte) error {
 	}
 	return nil
 }
-func (m *Overflow) UnmarshalVT(dAtA []byte) error {
-	l := len(dAtA)
-	iNdEx := 0
-	for iNdEx < l {
-		preIndex := iNdEx
-		var wire uint64
-		for shift := uint(0); ; shift += 7 {
-			if shift >= 64 {
-				return ErrIntOverflow
-			}
-			if iNdEx >= l {
-				return io.ErrUnexpectedEOF
-			}
-			b := dAtA[iNdEx]
-			iNdEx++
-			wire |= uint64(b&0x7F) << shift
-			if b < 0x80 {
-				break
-			}
-		}
-		fieldNum := int32(wire >> 3)
-		wireType := int(wire & 0x7)
-		if wireType == 4 {
-			return fmt.Errorf("proto: Overflow: wiretype end group for non-group")
-		}
-		if fieldNum <= 0 {
-			return fmt.Errorf("proto: Overflow: illegal tag %d (wire type %d)", fieldNum, wire)
-		}
-		switch fieldNum {
-		case 1:
-			if wireType != 2 {
-				return fmt.Errorf("proto: wrong wireType = %d for field OverflowTransactions", wireType)
-			}
-			var msglen int
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflow
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				msglen |= int(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-			if msglen < 0 {
-				return ErrInvalidLength
-			}
-			postIndex := iNdEx + msglen
-			if postIndex < 0 {
-				return ErrInvalidLength
-			}
-			if postIndex > l {
-				return io.ErrUnexpectedEOF
-			}
-			if m.OverflowTransactions == nil {
-				m.OverflowTransactions = TransactionMetricsFromVTPool()
-			}
-			if err := m.OverflowTransactions.UnmarshalVT(dAtA[iNdEx:postIndex]); err != nil {
-				return err
-			}
-			iNdEx = postIndex
-		case 2:
-			if wireType != 2 {
-				return fmt.Errorf("proto: wrong wireType = %d for field OverflowServiceTransactions", wireType)
-			}
-			var msglen int
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflow
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				msglen |= int(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-			if msglen < 0 {
-				return ErrInvalidLength
-			}
-			postIndex := iNdEx + msglen
-			if postIndex < 0 {
-				return ErrInvalidLength
-			}
-			if postIndex > l {
-				return io.ErrUnexpectedEOF
-			}
-			if m.OverflowServiceTransactions == nil {
-				m.OverflowServiceTransactions = ServiceTransactionMetricsFromVTPool()
-			}
-			if err := m.OverflowServiceTransactions.UnmarshalVT(dAtA[iNdEx:postIndex]); err != nil {
-				return err
-			}
-			iNdEx = postIndex
-		case 3:
-			if wireType != 2 {
-				return fmt.Errorf("proto: wrong wireType = %d for field OverflowSpans", wireType)
-			}
-			var msglen int
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflow
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				msglen |= int(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-			if msglen < 0 {
-				return ErrInvalidLength
-			}
-			postIndex := iNdEx + msglen
-			if postIndex < 0 {
-				return ErrInvalidLength
-			}
-			if postIndex > l {
-				return io.ErrUnexpectedEOF
-			}
-			if m.OverflowSpans == nil {
-				m.OverflowSpans = SpanMetricsFromVTPool()
-			}
-			if err := m.OverflowSpans.UnmarshalVT(dAtA[iNdEx:postIndex]); err != nil {
-				return err
-			}
-			iNdEx = postIndex
-		case 4:
-			if wireType != 2 {
-				return fmt.Errorf("proto: wrong wireType = %d for field OverflowTransactionsEstimator", wireType)
-			}
-			var byteLen int
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflow
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				byteLen |= int(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-			if byteLen < 0 {
-				return ErrInvalidLength
-			}
-			postIndex := iNdEx + byteLen
-			if postIndex < 0 {
-				return ErrInvalidLength
-			}
-			if postIndex > l {
-				return io.ErrUnexpectedEOF
-			}
-			m.OverflowTransactionsEstimator = append(m.OverflowTransactionsEstimator[:0], dAtA[iNdEx:postIndex]...)
-			if m.OverflowTransactionsEstimator == nil {
-				m.OverflowTransactionsEstimator = []byte{}
-			}
-			iNdEx = postIndex
-		case 5:
-			if wireType != 2 {
-				return fmt.Errorf("proto: wrong wireType = %d for field OverflowServiceTransactionsEstimator", wireType)
-			}
-			var byteLen int
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflow
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				byteLen |= int(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-			if byteLen < 0 {
-				return ErrInvalidLength
-			}
-			postIndex := iNdEx + byteLen
-			if postIndex < 0 {
-				return ErrInvalidLength
-			}
-			if postIndex > l {
-				return io.ErrUnexpectedEOF
-			}
-			m.OverflowServiceTransactionsEstimator = append(m.OverflowServiceTransactionsEstimator[:0], dAtA[iNdEx:postIndex]...)
-			if m.OverflowServiceTransactionsEstimator == nil {
-				m.OverflowServiceTransactionsEstimator = []byte{}
-			}
-			iNdEx = postIndex
-		case 6:
-			if wireType != 2 {
-				return fmt.Errorf("proto: wrong wireType = %d for field OverflowSpansEstimator", wireType)
-			}
-			var byteLen int
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflow
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				byteLen |= int(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-			if byteLen < 0 {
-				return ErrInvalidLength
-			}
-			postIndex := iNdEx + byteLen
-			if postIndex < 0 {
-				return ErrInvalidLength
-			}
-			if postIndex > l {
-				return io.ErrUnexpectedEOF
-			}
-			m.OverflowSpansEstimator = append(m.OverflowSpansEstimator[:0], dAtA[iNdEx:postIndex]...)
-			if m.OverflowSpansEstimator == nil {
-				m.OverflowSpansEstimator = []byte{}
-			}
-			iNdEx = postIndex
-		default:
-			iNdEx = preIndex
-			skippy, err := skip(dAtA[iNdEx:])
-			if err != nil {
-				return err
-			}
-			if (skippy < 0) || (iNdEx+skippy) < 0 {
-				return ErrInvalidLength
-			}
-			if (iNdEx + skippy) > l {
-				return io.ErrUnexpectedEOF
-			}
-			m.unknownFields = append(m.unknownFields, dAtA[iNdEx:iNdEx+skippy]...)
-			iNdEx += skippy
-		}
-	}
-
-	if iNdEx > l {
-		return io.ErrUnexpectedEOF
-	}
-	return nil
-}
 
 func skip(dAtA []byte) (n int, err error) {
 	l := len(dAtA)
diff --git a/aggregators/codec.go b/aggregators/codec.go
index e1e81ba..2b1d345 100644
--- a/aggregators/codec.go
+++ b/aggregators/codec.go
@@ -427,9 +427,7 @@ func histogramFromProto(h *hdrhistogram.HistogramRepresentation, pb *aggregation
 	h.CountsRep.Reset()
 
 	for i := 0; i < len(pb.Buckets); i++ {
-		bucket := pb.Buckets[i]
-		counts := pb.Counts[i]
-		h.CountsRep.Add(bucket, counts)
+		h.CountsRep.Add(pb.Buckets[i], pb.Counts[i])
 	}
 }
 
@@ -455,9 +453,9 @@ func setHistogramProto(h *hdrhistogram.HistogramRepresentation, pb *aggregationp
 	if countsLen > cap(pb.Counts) {
 		pb.Counts = make([]int64, 0, countsLen)
 	}
-	h.CountsRep.ForEach(func(bucket int32, value int64) {
+	h.CountsRep.ForEach(func(bucket int32, count int64) {
 		pb.Buckets = append(pb.Buckets, bucket)
-		pb.Counts = append(pb.Counts, value)
+		pb.Counts = append(pb.Counts, count)
 	})
 }
 
diff --git a/aggregators/internal/hdrhistogram/hdrhistogram.go b/aggregators/internal/hdrhistogram/hdrhistogram.go
index b277134..7f91f94 100644
--- a/aggregators/internal/hdrhistogram/hdrhistogram.go
+++ b/aggregators/internal/hdrhistogram/hdrhistogram.go
@@ -33,6 +33,8 @@ import (
 	"math"
 	"math/bits"
 	"time"
+
+	"golang.org/x/exp/slices"
 )
 
 const (
@@ -120,24 +122,21 @@ func (h *HistogramRepresentation) Buckets() (int64, []int64, []float64) {
 	values := make([]float64, 0, h.CountsRep.Len())
 
 	var totalCount int64
-	var bucketsSeen int
+	var prevBucket int32
 	iter := h.iterator()
-	// TODO @lahsivjar: Assuming sparse representation, we might be better off
-	// by sorting CountsRep rather than what we do now to avoid sorting.
-	for idx := 0; iter.next(); idx++ {
-		if bucketsSeen == h.CountsRep.Len() {
-			break
+	iter.nextCountAtIdx()
+	h.CountsRep.ForEach(func(bucket int32, scaledCounts int64) {
+		if scaledCounts <= 0 {
+			return
 		}
-		scaledCount, ok := h.CountsRep.Get(int32(idx))
-		if !ok || scaledCount <= 0 {
-			continue
+		if iter.advance(int(bucket - prevBucket)) {
+			count := int64(math.Round(float64(scaledCounts) / histogramCountScale))
+			counts = append(counts, count)
+			values = append(values, float64(iter.highestEquivalentValue))
+			totalCount += count
 		}
-		bucketsSeen++
-		count := int64(math.Round(float64(scaledCount) / histogramCountScale))
-		counts = append(counts, count)
-		values = append(values, float64(iter.highestEquivalentValue))
-		totalCount += count
-	}
+		prevBucket = bucket
+	})
 	return totalCount, counts, values
 }
 
@@ -203,9 +202,12 @@ type iterator struct {
 	highestEquivalentValue  int64
 }
 
-func (i *iterator) next() bool {
-	if !i.nextCountAtIdx() {
-		return false
+// advance advances the iterator by count
+func (i *iterator) advance(count int) bool {
+	for c := 0; c < count; c++ {
+		if !i.nextCountAtIdx() {
+			return false
+		}
 	}
 	i.highestEquivalentValue = i.h.highestEquivalentValue(i.valueFromIdx)
 	return true
@@ -280,46 +282,59 @@ func getBucketCount() int32 {
 	return bucketsNeeded
 }
 
+// bar represents a bar of histogram. Each bar has a bucket, representing
+// where the bar belongs to in the histogram range, and the count of values
+// in each bucket.
+type bar struct {
+	Bucket int32
+	Count  int64
+}
+
 // HybridCountsRep represents a hybrid counts representation for
 // sparse histogram. It is optimized to record a single value as
 // integer type and more values as map.
 type HybridCountsRep struct {
 	bucket int32
 	value  int64
-	m      map[int32]int64
+	s      []bar
 }
 
 // Add adds a new value to a bucket of given index.
 func (c *HybridCountsRep) Add(bucket int32, value int64) {
-	if c.m == nil && c.bucket == 0 && c.value == 0 {
+	if c.s == nil && c.bucket == 0 && c.value == 0 {
 		c.bucket = bucket
 		c.value = value
 		return
 	}
-	if c.m == nil {
-		c.m = make(map[int32]int64)
-		// automatic promotion to map
-		c.m[c.bucket] = c.value
+	if c.s == nil {
+		// automatic promotion to slice
+		c.s = make([]bar, 0, 128) // TODO: Use pool
+		c.s = slices.Insert(c.s, 0, bar{Bucket: c.bucket, Count: c.value})
 		c.bucket, c.value = 0, 0
 	}
-	c.m[bucket] += value
+	at, found := slices.BinarySearchFunc(c.s, bar{Bucket: bucket}, compareBar)
+	if found {
+		c.s[at].Count += value
+		return
+	}
+	c.s = slices.Insert(c.s, at, bar{Bucket: bucket, Count: value})
 }
 
 // ForEach iterates over each bucket and calls the given function.
 func (c *HybridCountsRep) ForEach(f func(int32, int64)) {
-	if c.m == nil && (c.bucket != 0 || c.value != 0) {
+	if c.s == nil && (c.bucket != 0 || c.value != 0) {
 		f(c.bucket, c.value)
 		return
 	}
-	for k, v := range c.m {
-		f(k, v)
+	for i := range c.s {
+		f(c.s[i].Bucket, c.s[i].Count)
 	}
 }
 
 // Len returns the number of buckets currently recording.
 func (c *HybridCountsRep) Len() int {
-	if c.m != nil {
-		return len(c.m)
+	if c.s != nil {
+		return len(c.s)
 	}
 	if c.bucket != 0 || c.value != 0 {
 		return 1
@@ -330,23 +345,24 @@ func (c *HybridCountsRep) Len() int {
 // Get returns the count of values in a given bucket along with a bool
 // which is false if the bucket is not found.
 func (c *HybridCountsRep) Get(bucket int32) (int64, bool) {
-	if c.m == nil {
+	if c.s == nil {
 		if c.bucket == bucket {
 			return c.value, true
 		}
 		return 0, false
 	}
-	val, ok := c.m[bucket]
-	return val, ok
+	at, found := slices.BinarySearchFunc(c.s, bar{Bucket: bucket}, compareBar)
+	if found {
+		return c.s[at].Count, true
+	}
+	return 0, false
 }
 
 // Reset resets the values recorded.
 func (c *HybridCountsRep) Reset() {
 	c.bucket = 0
 	c.value = 0
-	for k := range c.m {
-		delete(c.m, k)
-	}
+	c.s = c.s[:0]
 }
 
 // Equal returns true if same bucket and count is recorded in both.
@@ -366,3 +382,13 @@ func (c *HybridCountsRep) Equal(h *HybridCountsRep) bool {
 	})
 	return equal
 }
+
+func compareBar(a, b bar) int {
+	if a.Bucket == b.Bucket {
+		return 0
+	}
+	if a.Bucket > b.Bucket {
+		return 1
+	}
+	return -1
+}
diff --git a/aggregators/merger.go b/aggregators/merger.go
index 3f76f7e..98224f0 100644
--- a/aggregators/merger.go
+++ b/aggregators/merger.go
@@ -6,9 +6,9 @@ package aggregators
 
 import (
 	"io"
-	"sync"
 
 	"github.com/axiomhq/hyperloglog"
+	"golang.org/x/exp/slices"
 
 	"github.com/elastic/apm-aggregation/aggregationpb"
 )
@@ -407,39 +407,68 @@ func mergeSpanMetrics(to, from *aggregationpb.SpanMetrics) {
 	to.Sum += from.Sum
 }
 
-// mapPool is a pool of maps to facilitate histogram merges.
-var mapPool = sync.Pool{New: func() interface{} {
-	return make(map[int32]int64)
-}}
-
+// mergeHistogram merges two proto representation of HDRHistogram. The
+// merge assumes both histograms are created with same arguments and
+// their representations are sorted by bucket.
 func mergeHistogram(to, from *aggregationpb.HDRHistogram) {
-	// Assume both histograms are created with same arguments
-	m := mapPool.Get().(map[int32]int64)
-	defer mapPool.Put(m)
-	for k := range m {
-		delete(m, k)
+	if len(from.Buckets) == 0 {
+		return
 	}
 
-	for i := 0; i < len(to.Buckets); i++ {
-		m[to.Buckets[i]] = to.Counts[i]
-	}
-	for i := 0; i < len(from.Buckets); i++ {
-		m[from.Buckets[i]] += from.Counts[i]
+	if len(to.Buckets) == 0 {
+		to.Buckets = append(to.Buckets, from.Buckets...)
+		to.Counts = append(to.Counts, from.Counts...)
+		return
 	}
 
-	if cap(to.Buckets) < len(m) {
-		to.Buckets = make([]int32, len(m))
-	}
-	if cap(to.Counts) < len(m) {
-		to.Counts = make([]int64, len(m))
+	requiredLen := len(to.Buckets) + len(from.Buckets)
+	for toIdx, fromIdx := 0, 0; toIdx < len(to.Buckets) && fromIdx < len(from.Buckets); {
+		v := to.Buckets[toIdx] - from.Buckets[fromIdx]
+		switch {
+		case v == 0:
+			// For every bucket that is common, we need one less bucket in final slice
+			requiredLen--
+			toIdx++
+			fromIdx++
+		case v < 0:
+			toIdx++
+		case v > 0:
+			fromIdx++
+		}
 	}
 
-	to.Buckets = to.Buckets[:0]
-	to.Counts = to.Counts[:0]
-
-	for b, c := range m {
-		to.Buckets = append(to.Buckets, b)
-		to.Counts = append(to.Counts, c)
+	toIdx, fromIdx := len(to.Buckets)-1, len(from.Buckets)-1
+	to.Buckets = slices.Grow(to.Buckets, requiredLen)
+	to.Counts = slices.Grow(to.Counts, requiredLen)
+	to.Buckets = to.Buckets[:requiredLen]
+	to.Counts = to.Counts[:requiredLen]
+	for idx := len(to.Buckets) - 1; idx >= 0; idx-- {
+		if fromIdx < 0 {
+			break
+		}
+		if toIdx < 0 {
+			to.Counts[idx] = from.Counts[fromIdx]
+			to.Buckets[idx] = from.Buckets[fromIdx]
+			fromIdx--
+			continue
+		}
+		v := to.Buckets[toIdx] - from.Buckets[fromIdx]
+		switch {
+		case v == 0:
+			to.Counts[toIdx] += from.Counts[fromIdx]
+			to.Counts[idx] = to.Counts[toIdx]
+			to.Buckets[idx] = to.Buckets[toIdx]
+			toIdx--
+			fromIdx--
+		case v > 0:
+			to.Counts[idx] = to.Counts[toIdx]
+			to.Buckets[idx] = to.Buckets[toIdx]
+			toIdx--
+		case v < 0:
+			to.Counts[idx] = from.Counts[fromIdx]
+			to.Buckets[idx] = from.Buckets[fromIdx]
+			fromIdx--
+		}
 	}
 }
 
diff --git a/aggregators/merger_test.go b/aggregators/merger_test.go
index 686e759..7a9008c 100644
--- a/aggregators/merger_test.go
+++ b/aggregators/merger_test.go
@@ -999,26 +999,66 @@ func TestCardinalityEstimationOnSubKeyCollision(t *testing.T) {
 }
 
 func TestMergeHistogram(t *testing.T) {
-	// Test assumes histogram representation Merge is correct
-	hist1, hist2 := hdrhistogram.New(), hdrhistogram.New()
-
-	for i := 0; i < 1_000_000; i++ {
-		v1, v2 := rand.Int63n(3_600_000_000), rand.Int63n(3_600_000_000)
-		c1, c2 := rand.Int63n(1_000), rand.Int63n(1_000)
-		hist1.RecordValues(v1, c1)
-		hist2.RecordValues(v2, c2)
-	}
+	for _, tc := range []struct {
+		name       string
+		recordFunc func(h1, h2 *hdrhistogram.HistogramRepresentation)
+	}{
+		{
+			name: "zero_values",
+			recordFunc: func(h1, h2 *hdrhistogram.HistogramRepresentation) {
+				h1.RecordValues(0, 0)
+				h2.RecordValues(0, 0)
+			},
+		},
+		{
+			name: "random_only_to",
+			recordFunc: func(h1, h2 *hdrhistogram.HistogramRepresentation) {
+				for i := 0; i < 1_000_000; i++ {
+					v := rand.Int63n(3_600_000_000)
+					c := rand.Int63n(1_000)
+					h1.RecordValues(v, c)
+				}
+			},
+		},
+		{
+			name: "random_only_from",
+			recordFunc: func(h1, h2 *hdrhistogram.HistogramRepresentation) {
+				for i := 0; i < 1_000_000; i++ {
+					v := rand.Int63n(3_600_000_000)
+					c := rand.Int63n(1_000)
+					h2.RecordValues(v, c)
+				}
+			},
+		},
+		{
+			name: "random_both",
+			recordFunc: func(h1, h2 *hdrhistogram.HistogramRepresentation) {
+				for i := 0; i < 1_000_000; i++ {
+					v1, v2 := rand.Int63n(3_600_000_000), rand.Int63n(3_600_000_000)
+					c1, c2 := rand.Int63n(1_000), rand.Int63n(1_000)
+					h1.RecordValues(v1, c1)
+					h2.RecordValues(v2, c2)
+				}
+			},
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			// Test assumes histogram representation Merge is correct
+			hist1, hist2 := hdrhistogram.New(), hdrhistogram.New()
 
-	histproto1, histproto2 := histogramToProto(hist1), histogramToProto(hist2)
-	hist1.Merge(hist2)
-	mergeHistogram(histproto1, histproto2)
-	histActual := hdrhistogram.New()
-	histogramFromProto(histActual, histproto1)
+			tc.recordFunc(hist1, hist2)
+			histproto1, histproto2 := histogramToProto(hist1), histogramToProto(hist2)
+			hist1.Merge(hist2)
+			mergeHistogram(histproto1, histproto2)
+			histActual := hdrhistogram.New()
+			histogramFromProto(histActual, histproto1)
 
-	assert.Empty(t, cmp.Diff(
-		hist1,
-		histActual,
-		cmp.AllowUnexported(hdrhistogram.HistogramRepresentation{}),
-		cmp.AllowUnexported(hdrhistogram.HybridCountsRep{}),
-	))
+			assert.Empty(t, cmp.Diff(
+				hist1,
+				histActual,
+				cmp.AllowUnexported(hdrhistogram.HistogramRepresentation{}),
+				cmp.AllowUnexported(hdrhistogram.HybridCountsRep{}),
+			))
+		})
+	}
 }
diff --git a/go.mod b/go.mod
index 19f5556..e3d9d57 100644
--- a/go.mod
+++ b/go.mod
@@ -18,6 +18,7 @@ require (
 	go.opentelemetry.io/otel/sdk/metric v0.39.0
 	go.opentelemetry.io/otel/trace v1.16.0
 	go.uber.org/zap v1.24.0
+	golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1
 	golang.org/x/sync v0.3.0
 	google.golang.org/protobuf v1.31.0
 )
@@ -55,7 +56,6 @@ require (
 	go.elastic.co/fastjson v1.3.0 // indirect
 	go.uber.org/atomic v1.10.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
-	golang.org/x/exp v0.0.0-20230713183714-613f0c0eb8a1 // indirect
 	golang.org/x/sys v0.8.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	howett.net/plist v1.0.0 // indirect
diff --git a/proto/aggregation.proto b/proto/aggregation.proto
index 7e616cd..f6b2646 100644
--- a/proto/aggregation.proto
+++ b/proto/aggregation.proto
@@ -131,9 +131,13 @@ message SpanMetrics {
   double sum = 2;
 }
 
-message CountValue {
-  int64 count = 1;
-  int64 value = 2;
+message Overflow {
+  TransactionMetrics overflow_transactions = 1;
+  ServiceTransactionMetrics overflow_service_transactions = 2;
+  SpanMetrics overflow_spans = 3;
+  bytes overflow_transactions_estimator = 4;
+  bytes overflow_service_transactions_estimator = 5;
+  bytes overflow_spans_estimator = 6;
 }
 
 message HDRHistogram {
@@ -144,11 +148,3 @@ message HDRHistogram {
   repeated int32 buckets = 5;
 }
 
-message Overflow {
-  TransactionMetrics overflow_transactions = 1;
-  ServiceTransactionMetrics overflow_service_transactions = 2;
-  SpanMetrics overflow_spans = 3;
-  bytes overflow_transactions_estimator = 4;
-  bytes overflow_service_transactions_estimator = 5;
-  bytes overflow_spans_estimator = 6;
-}