diff --git a/pkg/sql/distsqlrun/backfiller.go b/pkg/sql/distsqlrun/backfiller.go
index f52ea6494e4b..a1dd1638b61b 100644
--- a/pkg/sql/distsqlrun/backfiller.go
+++ b/pkg/sql/distsqlrun/backfiller.go
@@ -43,6 +43,9 @@ type chunkBackfiller interface {
 		chunkSize int64,
 		readAsOf hlc.Timestamp,
 	) (roachpb.Key, error)
+
+	// flush writes any pending backfilled data into SSTs and flushes them.
+	flush(ctx context.Context, readAsOf hlc.Timestamp) error
 }
 
 // backfiller is a processor that implements a distributed backfill of
@@ -133,6 +136,11 @@ func (b *backfiller) mainLoop(ctx context.Context) error {
 			break
 		}
 	}
+
+	if err := b.flush(ctx, b.spec.ReadAsOf); err != nil {
+		return err
+	}
+
 	log.VEventf(ctx, 2, "processed %d rows in %d chunks", row, nChunks)
 	return WriteResumeSpan(ctx,
 		b.flowCtx.ClientDB,
diff --git a/pkg/sql/distsqlrun/columnbackfiller.go b/pkg/sql/distsqlrun/columnbackfiller.go
index f8213726cc95..3575d83429fc 100644
--- a/pkg/sql/distsqlrun/columnbackfiller.go
+++ b/pkg/sql/distsqlrun/columnbackfiller.go
@@ -105,3 +105,8 @@ func (cb *columnBackfiller) runChunk(
 	})
 	return key, err
 }
+
+// flush implements the chunkBackfiller interface.
+func (cb *columnBackfiller) flush(ctx context.Context, readAsOf hlc.Timestamp) error {
+	return nil
+}
diff --git a/pkg/sql/distsqlrun/indexbackfiller.go b/pkg/sql/distsqlrun/indexbackfiller.go
index 3c7b05c71d21..08f2850c0d3b 100644
--- a/pkg/sql/distsqlrun/indexbackfiller.go
+++ b/pkg/sql/distsqlrun/indexbackfiller.go
@@ -38,6 +38,9 @@ type indexBackfiller struct {
 	backfill.IndexBackfiller
 
 	desc *sqlbase.ImmutableTableDescriptor
+
+	// pending index entries that haven't yet been flushed.
+	entries []sqlbase.IndexEntry
 }
 
 var _ Processor = &indexBackfiller{}
@@ -112,7 +115,6 @@ func (ib *indexBackfiller) runChunk(
 		}
 	*/
 
-	start := timeutil.Now()
 	var entries []sqlbase.IndexEntry
 	if err := ib.flowCtx.ClientDB.Txn(ctx, func(ctx context.Context, txn *client.Txn) error {
 		txn.SetFixedTimestamp(ctx, readAsOf)
@@ -124,56 +126,10 @@ func (ib *indexBackfiller) runChunk(
 	}); err != nil {
 		return nil, err
 	}
-	prepTime := timeutil.Now().Sub(start)
 
 	enabled := backfill.BulkWriteIndex.Get(&ib.flowCtx.Settings.SV)
 	if enabled {
-		start := timeutil.Now()
-		sort.Slice(entries, func(i, j int) bool {
-			return entries[i].Key.Compare(entries[j].Key) < 0
-		})
-		sortTime := timeutil.Now().Sub(start)
-
-		start = timeutil.Now()
-		adder, err := ib.flowCtx.BulkAdder(ctx, ib.flowCtx.ClientDB, 32<<20, readAsOf)
-		if err != nil {
-			return nil, err
-		}
-		defer adder.Close()
-		containsInvertedIndex := ib.ContainsInvertedIndex()
-		for i := range entries {
-			if err := adder.Add(ctx, entries[i].Key, entries[i].Value.RawBytes); err != nil {
-				// Detect a duplicate within the SST being constructed. This is an
-				// insufficient but useful method for unique constraint enforcement
-				// and the index has to be validated after construction.
-				if i > 0 && entries[i-1].Key.Equal(entries[i].Key) {
-					if containsInvertedIndex {
-						// Depend on post index backfill validation to catch any errors.
-						continue
-					}
-					desc, err := ib.desc.MakeFirstMutationPublic()
-					immutable := sqlbase.NewImmutableTableDescriptor(*desc.TableDesc())
-					if err != nil {
-						return nil, err
-					}
-					entry := entries[i]
-					return nil, row.NewUniquenessConstraintViolationError(
-						ctx, immutable, entry.Key, &entry.Value)
-				}
-				return nil, err
-			}
-		}
-		addTime := timeutil.Now().Sub(start)
-
-		if err := adder.Flush(ctx); err != nil {
-			return nil, err
-		}
-
-		// Don't log perf stats in tests with small indexes.
-		if len(entries) > 1000 {
-			log.Infof(ctx, "index backfill stats: entries %d, prepare %+v, sort %+v, add-sst %+v",
-				len(entries), prepTime, sortTime, addTime)
-		}
+		ib.entries = append(ib.entries, entries...)
 		return key, nil
 	}
 	retried := false
@@ -224,3 +180,56 @@ func (ib *indexBackfiller) runChunk(
 
 	return key, nil
 }
+
+func (ib *indexBackfiller) flush(ctx context.Context, readAsOf hlc.Timestamp) error {
+	if len(ib.entries) > 0 {
+		entries := ib.entries
+		ib.entries = nil
+		start := timeutil.Now()
+		sort.Slice(entries, func(i, j int) bool {
+			return entries[i].Key.Compare(entries[j].Key) < 0
+		})
+		sortTime := timeutil.Now().Sub(start)
+
+		start = timeutil.Now()
+		adder, err := ib.flowCtx.BulkAdder(ctx, ib.flowCtx.ClientDB, 32<<20, readAsOf)
+		if err != nil {
+			return err
+		}
+		defer adder.Close()
+		containsInvertedIndex := ib.ContainsInvertedIndex()
+		for i := range entries {
+			if err := adder.Add(ctx, entries[i].Key, entries[i].Value.RawBytes); err != nil {
+				// Detect a duplicate within the SST being constructed. This is an
+				// insufficient but useful method for unique constraint enforcement
+				// and the index has to be validated after construction.
+				if i > 0 && entries[i-1].Key.Equal(entries[i].Key) {
+					if containsInvertedIndex {
+						// Depend on post index backfill validation to catch any errors.
+						continue
+					}
+					desc, err := ib.desc.MakeFirstMutationPublic()
+					immutable := sqlbase.NewImmutableTableDescriptor(*desc.TableDesc())
+					if err != nil {
+						return err
+					}
+					entry := entries[i]
+					return row.NewUniquenessConstraintViolationError(
+						ctx, immutable, entry.Key, &entry.Value)
+				}
+				return err
+			}
+		}
+		addTime := timeutil.Now().Sub(start)
+
+		start = timeutil.Now()
+		if err := adder.Flush(ctx); err != nil {
+			return err
+		}
+		flushTime := timeutil.Now().Sub(start)
+
+		log.Infof(ctx, "index backfill stats: entries %d, sort %+v, add-sst %+v, flush %+v",
+			len(entries), sortTime, addTime, flushTime)
+	}
+	return nil
+}