diff --git a/model/error.go b/model/error.go
index bd0a1d30432..c16f8db3b3f 100644
--- a/model/error.go
+++ b/model/error.go
@@ -51,9 +51,9 @@ const (
 
 type Error struct {
 	ID            *string
-	TransactionID *string
-	TraceID       *string
-	ParentID      *string
+	TransactionID string
+	TraceID       string
+	ParentID      string
 
 	Timestamp time.Time
 	Metadata  Metadata
@@ -122,16 +122,18 @@ func (e *Error) Transform(ctx context.Context, tctx *transform.Context) []beat.E
 
 	// sampled and type is nil if an error happens outside a transaction or an (old) agent is not sending sampled info
 	// agents must send semantically correct data
-	if e.TransactionSampled != nil || e.TransactionType != nil || (e.TransactionID != nil && *e.TransactionID != "") {
+	if e.TransactionSampled != nil || e.TransactionType != nil || e.TransactionID != "" {
 		transaction := common.MapStr{}
-		utility.Set(transaction, "id", e.TransactionID)
+		if e.TransactionID != "" {
+			transaction["id"] = e.TransactionID
+		}
 		utility.Set(transaction, "type", e.TransactionType)
 		utility.Set(transaction, "sampled", e.TransactionSampled)
 		utility.Set(fields, "transaction", transaction)
 	}
 
-	utility.AddId(fields, "parent", e.ParentID)
-	utility.AddId(fields, "trace", e.TraceID)
+	utility.AddID(fields, "parent", e.ParentID)
+	utility.AddID(fields, "trace", e.TraceID)
 	utility.Set(fields, "timestamp", utility.TimeAsMicros(e.Timestamp))
 
 	return []beat.Event{
diff --git a/model/error_test.go b/model/error_test.go
index f907bdc976c..9ef038935f6 100644
--- a/model/error_test.go
+++ b/model/error_test.go
@@ -217,7 +217,7 @@ func TestEventFields(t *testing.T) {
 				Culprit:       &culprit,
 				Exception:     &exception,
 				Log:           &log,
-				TransactionID: &trID,
+				TransactionID: trID,
 
 				// Service name and version are required for sourcemapping.
 				Metadata: Metadata{
@@ -354,7 +354,7 @@ func TestEvents(t *testing.T) {
 					Message:    &exMsg,
 					Stacktrace: Stacktrace{&StacktraceFrame{Filename: tests.StringPtr("myFile")}},
 				},
-				TransactionID:      &trID,
+				TransactionID:      trID,
 				TransactionSampled: &sampledTrue,
 				Labels:             &labels,
 				Page:               &Page{Url: &url, Referer: &referer},
diff --git a/model/modeldecoder/error.go b/model/modeldecoder/error.go
index 17e3ca6b420..a65366493c4 100644
--- a/model/modeldecoder/error.go
+++ b/model/modeldecoder/error.go
@@ -77,12 +77,12 @@ func decodeError(input Input, schema *jsonschema.Schema) (*m.Error, error) {
 		Custom:             ctx.Custom,
 		Experimental:       ctx.Experimental,
 		Timestamp:          decoder.TimeEpochMicro(raw, "timestamp"),
-		TransactionID:      decoder.StringPtr(raw, fieldName("transaction_id")),
-		ParentID:           decoder.StringPtr(raw, fieldName("parent_id")),
-		TraceID:            decoder.StringPtr(raw, fieldName("trace_id")),
 		TransactionSampled: decoder.BoolPtr(raw, fieldName("sampled"), fieldName("transaction")),
 		TransactionType:    decoder.StringPtr(raw, fieldName("type"), fieldName("transaction")),
 	}
+	decodeString(raw, fieldName("parent_id"), &e.ParentID)
+	decodeString(raw, fieldName("trace_id"), &e.TraceID)
+	decodeString(raw, fieldName("transaction_id"), &e.TransactionID)
 
 	ex := decoder.MapStr(raw, fieldName("exception"))
 	e.Exception = decodeException(&decoder, input.Config.HasShortFieldNames)(ex)
diff --git a/model/modeldecoder/error_test.go b/model/modeldecoder/error_test.go
index 53c3363a8cf..243b8640f06 100644
--- a/model/modeldecoder/error_test.go
+++ b/model/modeldecoder/error_test.go
@@ -217,11 +217,11 @@ func TestErrorEventDecode(t *testing.T) {
 					},
 				},
 				ID:                 &id,
-				TransactionID:      &transactionID,
+				TransactionID:      transactionID,
 				TransactionSampled: &transactionSampled,
 				TransactionType:    &transactionType,
-				ParentID:           &parentID,
-				TraceID:            &traceID,
+				ParentID:           parentID,
+				TraceID:            traceID,
 				Culprit:            &culprit,
 			},
 		},
diff --git a/model/modeldecoder/span.go b/model/modeldecoder/span.go
index 5750b2f91e5..f5688d9ec14 100644
--- a/model/modeldecoder/span.go
+++ b/model/modeldecoder/span.go
@@ -37,14 +37,15 @@ var (
 	rumV3SpanSchema = validation.CreateSchema(schema.RUMV3Schema, "span")
 )
 
-// decodeRUMV3Span decodes a v3 RUM span.
-func decodeRUMV3Span(input Input) (*model.Span, error) {
+// decodeRUMV3Span decodes a v3 RUM span, and optional parent index.
+// If parent index wasn't specified, then the value will be negative.
+func decodeRUMV3Span(input Input) (_ *model.Span, parentIndex int, _ error) {
 	return decodeSpan(input, rumV3SpanSchema)
 }
 
 // DecodeSpan decodes a span.
 func DecodeSpan(input Input, batch *model.Batch) error {
-	span, err := decodeSpan(input, spanSchema)
+	span, _, err := decodeSpan(input, spanSchema)
 	if err != nil {
 		return err
 	}
@@ -52,10 +53,10 @@ func DecodeSpan(input Input, batch *model.Batch) error {
 	return nil
 }
 
-func decodeSpan(input Input, schema *jsonschema.Schema) (*model.Span, error) {
+func decodeSpan(input Input, schema *jsonschema.Schema) (_ *model.Span, parentIndex int, _ error) {
 	raw, err := validation.ValidateObject(input.Raw, schema)
 	if err != nil {
-		return nil, errors.Wrap(err, "failed to validate span")
+		return nil, -1, errors.Wrap(err, "failed to validate span")
 	}
 
 	fieldName := field.Mapper(input.Config.HasShortFieldNames)
@@ -68,16 +69,14 @@ func decodeSpan(input Input, schema *jsonschema.Schema) (*model.Span, error) {
 		Sync:      decoder.BoolPtr(raw, fieldName("sync")),
 		Timestamp: decoder.TimeEpochMicro(raw, fieldName("timestamp")),
 		ID:        decoder.String(raw, fieldName("id")),
-		ParentID:  decoder.StringPtr(raw, "parent_id"),
 		ChildIDs:  decoder.StringArr(raw, "child_ids"),
-		// ParentIdx comes from RUM V3 payloads only, and used to populate ParentID
-		ParentIdx:     decoder.IntPtr(raw, fieldName("parent_idx")),
-		TraceID:       decoder.StringPtr(raw, "trace_id"),
-		TransactionID: decoder.StringPtr(raw, "transaction_id"),
-		Type:          decoder.String(raw, fieldName("type")),
-		Subtype:       decoder.StringPtr(raw, fieldName("subtype")),
-		Action:        decoder.StringPtr(raw, fieldName("action")),
+		Type:      decoder.String(raw, fieldName("type")),
+		Subtype:   decoder.StringPtr(raw, fieldName("subtype")),
+		Action:    decoder.StringPtr(raw, fieldName("action")),
 	}
+	decodeString(raw, fieldName("parent_id"), &event.ParentID)
+	decodeString(raw, fieldName("trace_id"), &event.TraceID)
+	decodeString(raw, fieldName("transaction_id"), &event.TransactionID)
 
 	ctx := decoder.MapStr(raw, fieldName("context"))
 	if ctx != nil {
@@ -87,19 +86,19 @@ func decodeSpan(input Input, schema *jsonschema.Schema) (*model.Span, error) {
 
 		db, err := decodeDB(ctx, decoder.Err)
 		if err != nil {
-			return nil, err
+			return nil, -1, err
 		}
 		event.DB = db
 
 		http, err := decodeSpanHTTP(ctx, input.Config.HasShortFieldNames, decoder.Err)
 		if err != nil {
-			return nil, err
+			return nil, -1, err
 		}
 		event.HTTP = http
 
 		dest, destService, err := decodeDestination(ctx, input.Config.HasShortFieldNames, decoder.Err)
 		if err != nil {
-			return nil, err
+			return nil, -1, err
 		}
 		event.Destination = dest
 		event.DestinationService = destService
@@ -111,7 +110,7 @@ func decodeSpan(input Input, schema *jsonschema.Schema) (*model.Span, error) {
 		}
 
 		if event.Message, err = decodeMessage(ctx, decoder.Err); err != nil {
-			return nil, err
+			return nil, -1, err
 		}
 
 		if input.Config.Experimental {
@@ -124,7 +123,7 @@ func decodeSpan(input Input, schema *jsonschema.Schema) (*model.Span, error) {
 	var stacktr *m.Stacktrace
 	stacktr, decoder.Err = decodeStacktrace(raw[fieldName("stacktrace")], input.Config.HasShortFieldNames, decoder.Err)
 	if decoder.Err != nil {
-		return nil, decoder.Err
+		return nil, -1, decoder.Err
 	}
 	if stacktr != nil {
 		event.Stacktrace = *stacktr
@@ -152,7 +151,13 @@ func decodeSpan(input Input, schema *jsonschema.Schema) (*model.Span, error) {
 		event.Timestamp = timestamp
 	}
 
-	return &event, nil
+	// parent_idx comes from RUM V3 payloads only. It is used only during
+	// decoding to populate ParentID. We initialise to -1 to indicate lack
+	// of parent index.
+	parentIndex = -1
+	decodeInt(raw, fieldName("parent_idx"), &parentIndex)
+
+	return &event, parentIndex, nil
 }
 
 func decodeDB(input interface{}, err error) (*model.DB, error) {
diff --git a/model/modeldecoder/span_test.go b/model/modeldecoder/span_test.go
index 420990dde2d..9a9ed39adfd 100644
--- a/model/modeldecoder/span_test.go
+++ b/model/modeldecoder/span_test.go
@@ -98,9 +98,9 @@ func TestDecodeSpan(t *testing.T) {
 				Action:    &action2,
 				Duration:  duration,
 				Timestamp: spanTime,
-				ParentID:  &parentID,
+				ParentID:  parentID,
 				ID:        id,
-				TraceID:   &traceID,
+				TraceID:   traceID,
 			},
 		},
 		"no timestamp specified, request time + start used": {
@@ -113,9 +113,9 @@ func TestDecodeSpan(t *testing.T) {
 				Name:      name,
 				Type:      "db",
 				Duration:  duration,
-				ParentID:  &parentID,
+				ParentID:  parentID,
 				ID:        id,
-				TraceID:   &traceID,
+				TraceID:   traceID,
 				Start:     &start,
 				Timestamp: requestTime.Add(time.Duration(start * float64(time.Millisecond))),
 			},
@@ -135,10 +135,10 @@ func TestDecodeSpan(t *testing.T) {
 				Start:         &start,
 				Duration:      duration,
 				Timestamp:     spanTime,
-				ParentID:      &parentID,
+				ParentID:      parentID,
 				ID:            id,
-				TraceID:       &traceID,
-				TransactionID: &transactionID,
+				TraceID:       traceID,
+				TransactionID: transactionID,
 			},
 		},
 		"event experimental=true, no experimental payload": {
@@ -156,10 +156,10 @@ func TestDecodeSpan(t *testing.T) {
 				Start:         &start,
 				Duration:      duration,
 				Timestamp:     spanTime,
-				ParentID:      &parentID,
+				ParentID:      parentID,
 				ID:            id,
-				TraceID:       &traceID,
-				TransactionID: &transactionID,
+				TraceID:       traceID,
+				TransactionID: transactionID,
 			},
 			cfg: Config{Experimental: true},
 		},
@@ -178,10 +178,10 @@ func TestDecodeSpan(t *testing.T) {
 				Start:         &start,
 				Duration:      duration,
 				Timestamp:     spanTime,
-				ParentID:      &parentID,
+				ParentID:      parentID,
 				ID:            id,
-				TraceID:       &traceID,
-				TransactionID: &transactionID,
+				TraceID:       traceID,
+				TransactionID: transactionID,
 				Experimental:  123,
 			},
 			cfg: Config{Experimental: true},
@@ -206,9 +206,9 @@ func TestDecodeSpan(t *testing.T) {
 				},
 				Labels:        common.MapStr{"a": "tag", "tag_key": 17},
 				ID:            id,
-				TraceID:       &traceID,
-				ParentID:      &parentID,
-				TransactionID: &transactionID,
+				TraceID:       traceID,
+				ParentID:      parentID,
+				TransactionID: transactionID,
 				HTTP:          &m.HTTP{Method: &method, StatusCode: &statusCode, URL: &url},
 				DB: &m.DB{
 					Instance:     &instance,
diff --git a/model/modeldecoder/transaction.go b/model/modeldecoder/transaction.go
index 59a7e9130ce..bbd5c296587 100644
--- a/model/modeldecoder/transaction.go
+++ b/model/modeldecoder/transaction.go
@@ -95,7 +95,7 @@ func decodeRUMV3Spans(raw map[string]interface{}, input Input, tr *model.Transac
 	rawSpans := decoder.InterfaceArr(raw, fieldName("span"))
 	var spans = make([]*model.Span, len(rawSpans))
 	for idx, rawSpan := range rawSpans {
-		span, err := decodeRUMV3Span(Input{
+		span, parentIndex, err := decodeRUMV3Span(Input{
 			Raw:         rawSpan,
 			RequestTime: input.RequestTime,
 			Metadata:    input.Metadata,
@@ -104,12 +104,12 @@ func decodeRUMV3Spans(raw map[string]interface{}, input Input, tr *model.Transac
 		if err != nil {
 			return spans, err
 		}
-		span.TransactionID = &tr.ID
-		span.TraceID = &tr.TraceID
-		if span.ParentIdx == nil {
-			span.ParentID = &tr.ID
-		} else if *span.ParentIdx < idx {
-			span.ParentID = &spans[*span.ParentIdx].ID
+		span.TransactionID = tr.ID
+		span.TraceID = tr.TraceID
+		if parentIndex >= 0 && parentIndex < idx {
+			span.ParentID = spans[parentIndex].ID
+		} else {
+			span.ParentID = tr.ID
 		}
 		spans[idx] = span
 	}
@@ -158,12 +158,12 @@ func decodeTransaction(input Input, schema *jsonschema.Schema) (*model.Transacti
 		SpanCount: model.SpanCount{
 			Dropped: decoder.IntPtr(raw, fieldName("dropped"), fieldName("span_count")),
 			Started: decoder.IntPtr(raw, fieldName("started"), fieldName("span_count"))},
-		ParentID: decoder.StringPtr(raw, fieldName("parent_id")),
-		TraceID:  decoder.String(raw, fieldName("trace_id")),
+		TraceID: decoder.String(raw, fieldName("trace_id")),
 	}
 	if decoder.Err != nil {
 		return nil, decoder.Err
 	}
+	decodeString(raw, fieldName("parent_id"), &e.ParentID)
 	if e.Timestamp.IsZero() {
 		e.Timestamp = input.RequestTime
 	}
diff --git a/model/modeldecoder/transaction_test.go b/model/modeldecoder/transaction_test.go
index 41525df43f5..c96b15f3709 100644
--- a/model/modeldecoder/transaction_test.go
+++ b/model/modeldecoder/transaction_test.go
@@ -333,7 +333,7 @@ func TestTransactionEventDecode(t *testing.T) {
 				Type:      trType,
 				Name:      &name,
 				Result:    &result,
-				ParentID:  &parentID,
+				ParentID:  parentID,
 				TraceID:   traceID,
 				Duration:  duration,
 				Timestamp: timestampParsed,
diff --git a/model/span.go b/model/span.go
index 4fadc5a9cec..7d8d56c3cbb 100644
--- a/model/span.go
+++ b/model/span.go
@@ -45,11 +45,10 @@ var (
 type Span struct {
 	Metadata      Metadata
 	ID            string
-	TransactionID *string
-	ParentID      *string
+	TransactionID string
+	ParentID      string
 	ChildIDs      []string
-	ParentIdx     *int
-	TraceID       *string
+	TraceID       string
 
 	Timestamp time.Time
 
@@ -191,12 +190,12 @@ func (e *Span) Transform(ctx context.Context, tctx *transform.Context) []beat.Ev
 	utility.DeepUpdate(fields, "agent", e.Service.AgentFields())
 	// merges with metadata labels, overrides conflicting keys
 	utility.DeepUpdate(fields, "labels", e.Labels)
-	utility.AddId(fields, "parent", e.ParentID)
+	utility.AddID(fields, "parent", e.ParentID)
 	if e.ChildIDs != nil {
 		utility.Set(fields, "child", common.MapStr{"id": e.ChildIDs})
 	}
-	utility.AddId(fields, "trace", e.TraceID)
-	utility.AddId(fields, "transaction", e.TransactionID)
+	utility.AddID(fields, "trace", e.TraceID)
+	utility.AddID(fields, "transaction", e.TransactionID)
 	utility.Set(fields, "experimental", e.Experimental)
 	utility.Set(fields, "destination", e.Destination.fields())
 	utility.Set(fields, "timestamp", utility.TimeAsMicros(e.Timestamp))
diff --git a/model/span_test.go b/model/span_test.go
index cdc3d9f2ce8..6950b5ddc0f 100644
--- a/model/span_test.go
+++ b/model/span_test.go
@@ -73,8 +73,8 @@ func TestSpanTransform(t *testing.T) {
 			Span: Span{
 				Metadata:   metadata,
 				ID:         hexID,
-				TraceID:    &traceID,
-				ParentID:   &parentID,
+				TraceID:    traceID,
+				ParentID:   parentID,
 				Name:       "myspan",
 				Type:       "myspantype",
 				Subtype:    &subtype,
diff --git a/model/transaction.go b/model/transaction.go
index 8439da677ab..4e38e8cfa08 100644
--- a/model/transaction.go
+++ b/model/transaction.go
@@ -44,7 +44,7 @@ type Transaction struct {
 	Metadata Metadata
 
 	ID       string
-	ParentID *string
+	ParentID string
 	TraceID  string
 
 	Timestamp time.Time
@@ -120,8 +120,8 @@ func (e *Transaction) Transform(ctx context.Context, tctx *transform.Context) []
 	utility.Set(fields, "source", fields["client"])
 
 	// then merge event specific information
-	utility.AddId(fields, "parent", e.ParentID)
-	utility.AddId(fields, "trace", &e.TraceID)
+	utility.AddID(fields, "parent", e.ParentID)
+	utility.AddID(fields, "trace", e.TraceID)
 	utility.Set(fields, "timestamp", utility.TimeAsMicros(e.Timestamp))
 	// merges with metadata labels, overrides conflicting keys
 	utility.DeepUpdate(fields, "labels", e.Labels.Fields())
diff --git a/processor/otel/consumer.go b/processor/otel/consumer.go
index 47e67da09fd..c234f12fd05 100644
--- a/processor/otel/consumer.go
+++ b/processor/otel/consumer.go
@@ -111,7 +111,7 @@ func (c *Consumer) convert(td consumerdata.TraceData) *model.Batch {
 			transaction := model.Transaction{
 				Metadata:  md,
 				ID:        spanID,
-				ParentID:  &parentID,
+				ParentID:  parentID,
 				TraceID:   traceID,
 				Timestamp: startTime,
 				Duration:  duration,
@@ -128,8 +128,8 @@ func (c *Consumer) convert(td consumerdata.TraceData) *model.Batch {
 			span := model.Span{
 				Metadata:  md,
 				ID:        spanID,
-				ParentID:  &parentID,
-				TraceID:   &traceID,
+				ParentID:  parentID,
+				TraceID:   traceID,
 				Timestamp: startTime,
 				Duration:  duration,
 				Name:      name,
@@ -479,9 +479,9 @@ func parseErrors(logger *logp.Logger, source string, otelSpan *tracepb.Span) []*
 
 func addTransactionCtxToErr(transaction model.Transaction, err *model.Error) {
 	err.Metadata = transaction.Metadata
-	err.TransactionID = &transaction.ID
-	err.TraceID = &transaction.TraceID
-	err.ParentID = &transaction.ID
+	err.TransactionID = transaction.ID
+	err.TraceID = transaction.TraceID
+	err.ParentID = transaction.ID
 	err.HTTP = transaction.HTTP
 	err.URL = transaction.URL
 	err.TransactionType = &transaction.Type
@@ -491,7 +491,7 @@ func addSpanCtxToErr(span model.Span, hostname string, err *model.Error) {
 	err.Metadata = span.Metadata
 	err.TransactionID = span.TransactionID
 	err.TraceID = span.TraceID
-	err.ParentID = &span.ID
+	err.ParentID = span.ID
 	if span.HTTP != nil {
 		err.HTTP = &model.Http{}
 		if span.HTTP.StatusCode != nil {
diff --git a/utility/map_str_enhancer.go b/utility/map_str_enhancer.go
index 2cea3ad8e55..19983d26a0d 100644
--- a/utility/map_str_enhancer.go
+++ b/utility/map_str_enhancer.go
@@ -209,8 +209,8 @@ func Prune(m common.MapStr) common.MapStr {
 	return m
 }
 
-func AddId(fields common.MapStr, key string, id *string) {
-	if id != nil && *id != "" {
-		fields[key] = common.MapStr{"id": *id}
+func AddID(fields common.MapStr, key, id string) {
+	if id != "" {
+		fields[key] = common.MapStr{"id": id}
 	}
 }
diff --git a/x-pack/apm-server/aggregation/txmetrics/aggregator.go b/x-pack/apm-server/aggregation/txmetrics/aggregator.go
index a50109b9bc3..069558d9fbf 100644
--- a/x-pack/apm-server/aggregation/txmetrics/aggregator.go
+++ b/x-pack/apm-server/aggregation/txmetrics/aggregator.go
@@ -327,7 +327,7 @@ func makeTransactionAggregationKey(tx *model.Transaction) transactionAggregation
 		return ""
 	}
 	return transactionAggregationKey{
-		traceRoot:         tx.ParentID == nil,
+		traceRoot:         tx.ParentID == "",
 		transactionName:   deref(tx.Name),
 		transactionResult: deref(tx.Result),
 		transactionType:   tx.Type,