Scale the DAG

api-spec/openapi/swagger/ark/v1/indexer.openapi.json

@@ -1282,6 +1282,10 @@
             "type": "integer",
             "format": "int64"
           },
+          "depth": {
+            "type": "integer",
+            "format": "uint32"
+          },
           "expiresAt": {
             "type": "integer",
             "format": "int64"

api-spec/openapi/swagger/ark/v1/service.openapi.json

@@ -1436,6 +1436,10 @@
             "type": "integer",
             "format": "int64"
           },
+          "depth": {
+            "type": "integer",
+            "format": "uint32"
+          },
           "expiresAt": {
             "type": "integer",
             "format": "int64"

api-spec/openapi/swagger/ark/v1/types.openapi.json

@@ -410,6 +410,10 @@
             "type": "integer",
             "format": "int64"
           },
+          "depth": {
+            "type": "integer",
+            "format": "uint32"
+          },
           "expiresAt": {
             "type": "integer",
             "format": "int64"

api-spec/protobuf/ark/v1/indexer.proto

@@ -257,6 +257,7 @@ message IndexerVtxo {
   repeated string commitment_txids = 11;
   string settled_by = 12;
   string ark_txid = 13;
+  uint32 depth = 14;
 }
 
 message IndexerChain {

api-spec/protobuf/ark/v1/types.proto

@@ -28,6 +28,7 @@ message Vtxo {
   string spent_by = 11;
   string settled_by = 12;
   string ark_txid = 13;
+  uint32 depth = 14;
 }
 
 message TxData {

cmd/arkd/commands.go

@@ -156,9 +156,12 @@ var (
 		Name:  "update",
 		Usage: "Update the scheduled session configuration",
 		Flags: []cli.Flag{
-			scheduledSessionStartDateFlag, scheduledSessionEndDateFlag,
-			scheduledSessionDurationFlag, scheduledSessionPeriodFlag,
-			scheduledSessionRoundMinParticipantsCountFlag, scheduledSessionRoundMaxParticipantsCountFlag,
+			scheduledSessionStartDateFlag,
+			scheduledSessionEndDateFlag,
+			scheduledSessionDurationFlag,
+			scheduledSessionPeriodFlag,
+			scheduledSessionRoundMinParticipantsCountFlag,
+			scheduledSessionRoundMaxParticipantsCountFlag,
 		},
 		Action: updateScheduledSessionAction,
 	}

internal/core/application/fraud.go

@@ -61,7 +61,11 @@ func (s *service) reactToFraud(ctx context.Context, vtxo domain.Vtxo, mutx *sync
 					return
 				}
 			}
-			if err := s.sweeper.scheduleCheckpointSweep(vtxo.Outpoint, ptx, blockTimestamp); err != nil {
+			if err := s.sweeper.scheduleCheckpointSweep(
+				vtxo.Outpoint,
+				ptx,
+				blockTimestamp,
+			); err != nil {
 				log.Errorf("failed to schedule checkpoint sweep: %s", err)
 			}
 		}()

internal/core/application/indexer.go

@@ -239,8 +239,11 @@ func (i *indexerService) GetVtxoChain(
 	nextVtxos := []domain.Outpoint{vtxoKey}
 	visited := make(map[string]bool)
 
+	// Pre-fetch VTXOs using markers for optimization (reduces DB calls for deep chains)
+	vtxoCache := i.prefetchVtxosByMarkers(ctx, vtxoKey)
+
 	for len(nextVtxos) > 0 {
-		vtxos, err := i.repoManager.Vtxos().GetVtxos(ctx, nextVtxos)
+		vtxos, err := i.getVtxosFromCacheOrDB(ctx, nextVtxos, vtxoCache)
 		if err != nil {
 			return nil, err
 		}
@@ -369,6 +372,111 @@ func (i *indexerService) GetVtxoChain(
 	}, nil
 }
 
+// prefetchVtxosByMarkers pre-fetches VTXOs using markers for optimization.
+// This reduces the number of DB calls for deep chains by bulk fetching VTXOs
+// associated with the marker chain instead of fetching one at a time.
+func (i *indexerService) prefetchVtxosByMarkers(
+	ctx context.Context, startKey Outpoint,
+) map[string]domain.Vtxo {
+	// outpoint string -> VTXO cache
+	cache := make(map[string]domain.Vtxo)
+
+	if i.repoManager.Markers() == nil {
+		return cache
+	}
+
+	// Get starting VTXO to find its marker
+	startVtxos, err := i.repoManager.Vtxos().GetVtxos(ctx, []domain.Outpoint{startKey})
+	if err != nil || len(startVtxos) == 0 {
+		return cache
+	}
+
+	startVtxo := startVtxos[0]
+	// Add starting VTXO to cache
+	cache[startVtxo.Outpoint.String()] = startVtxo
+
+	if len(startVtxo.MarkerIDs) == 0 {
+		return cache
+	}
+
+	// Collect marker chain by following ParentMarkerIDs from all markers
+	markerIDs := make([]string, 0, len(startVtxo.MarkerIDs))
+	markerIDs = append(markerIDs, startVtxo.MarkerIDs...)
+
+	// Bob: we have to follow all parent markers because a vtxo can be associated with multiple markers if it was created at a depth that is a multiple of the marker interval. For example, if the marker interval is 100, a vtxo created at depth 200 would be associated with the markers at depth 100 and 200. To ensure we prefetch all relevant VTXOs, we need to follow all parent markers up the chain until we reach the root marker (depth 0).
+	// BFS to follow all parent markers
+	visited := make(map[string]bool)
+	for _, id := range startVtxo.MarkerIDs {
+		visited[id] = true
+	}
+
+	queue := make([]string, 0, len(startVtxo.MarkerIDs))
+	queue = append(queue, startVtxo.MarkerIDs...)
+
+	for len(queue) > 0 {
+		currentID := queue[0]
+		queue = queue[1:]
+
+		marker, err := i.repoManager.Markers().GetMarker(ctx, currentID)
+		if err != nil || marker == nil {
+			continue
+		}
+
+		for _, parentID := range marker.ParentMarkerIDs {
+			if !visited[parentID] {
+				visited[parentID] = true
+				markerIDs = append(markerIDs, parentID)
+				queue = append(queue, parentID)
+			}
+		}
+	}
+
+	// Bulk fetch VTXOs for all markers in the chain
+	vtxos, err := i.repoManager.Markers().GetVtxoChainByMarkers(ctx, markerIDs)
+	if err != nil {
+		return cache
+	}
+
+	for _, v := range vtxos {
+		cache[v.Outpoint.String()] = v
+	}
+
+	return cache
+}
+
+// getVtxosFromCacheOrDB retrieves VTXOs from cache first, falling back to DB for cache misses.
+// This is used in conjunction with prefetchVtxosByMarkers to reduce DB calls.
+func (i *indexerService) getVtxosFromCacheOrDB(
+	ctx context.Context,
+	outpoints []domain.Outpoint,
+	cache map[string]domain.Vtxo,
+) ([]domain.Vtxo, error) {
+	result := make([]domain.Vtxo, 0, len(outpoints))
+	missingOutpoints := make([]domain.Outpoint, 0)
+
+	for _, op := range outpoints {
+		if v, ok := cache[op.String()]; ok {
+			result = append(result, v)
+		} else {
+			missingOutpoints = append(missingOutpoints, op)
+		}
+	}
+
+	if len(missingOutpoints) > 0 {
+		dbVtxos, err := i.repoManager.Vtxos().GetVtxos(ctx, missingOutpoints)
+		if err != nil {
+			return nil, err
+		}
+		result = append(result, dbVtxos...)
+		// Add to cache for future lookups in this chain traversal
+		for _, v := range dbVtxos {
+			cache[v.Outpoint.String()] = v
+		}
+	}
+
+	return result, nil
+}
+
 func (i *indexerService) GetVirtualTxs(
 	ctx context.Context, txids []string, page *Page,
 ) (*VirtualTxsResp, error) {