diff --git a/internal/handlers/pg/msg_findandmodify.go b/internal/handlers/pg/msg_findandmodify.go
index a63af3470d21..9ff1cad87379 100644
--- a/internal/handlers/pg/msg_findandmodify.go
+++ b/internal/handlers/pg/msg_findandmodify.go
@@ -141,6 +141,7 @@ func (h *Handler) MsgFindAndModify(ctx context.Context, msg *wire.OpMsg) (*wire.
 					}
 				}
 
+				// TODO https://github.com/FerretDB/FerretDB/issues/2612
 				if _, err = updateDocument(ctx, tx, &qp, upsert); err != nil {
 					return lazyerrors.Error(err)
 				}
@@ -184,6 +185,7 @@ func (h *Handler) MsgFindAndModify(ctx context.Context, msg *wire.OpMsg) (*wire.
 				return nil
 			}
 
+			// TODO https://github.com/FerretDB/FerretDB/issues/2612
 			if _, err = deleteDocuments(ctx, dbPool, &qp, resDocs); err != nil {
 				return err
 			}
@@ -218,13 +220,14 @@ func upsertDocuments(ctx context.Context, dbPool *pgdb.Pool, tx pgx.Tx, docs []*
 
 	switch res.Operation {
 	case common.UpsertOperationInsert:
+		// TODO https://github.com/FerretDB/FerretDB/issues/2612
 		if err = insertDocument(ctx, tx, query, res.Upsert); err != nil {
 			return nil, lazyerrors.Error(err)
 		}
 
 		return res, nil
 	case common.UpsertOperationUpdate:
-
+		// TODO https://github.com/FerretDB/FerretDB/issues/2612
 		_, err = updateDocument(ctx, tx, query, res.Upsert)
 		if err != nil {
 			return nil, lazyerrors.Error(err)
diff --git a/internal/handlers/pg/msg_insert.go b/internal/handlers/pg/msg_insert.go
index 01fc8f940f4d..a26f4c4999b1 100644
--- a/internal/handlers/pg/msg_insert.go
+++ b/internal/handlers/pg/msg_insert.go
@@ -83,7 +83,7 @@ func insertMany(ctx context.Context, dbPool *pgdb.Pool, qp *pgdb.QueryParams, do
 	var inserted int32
 	var insErrors commonerrors.WriteErrors
 
-	//
+	// attempt to insert all documents in a single transaction
 	err := dbPool.InTransaction(ctx, func(tx pgx.Tx) error {
 		for i := 0; i < docs.Len(); i++ {
 			doc := must.NotFail(docs.Get(i))
@@ -101,7 +101,7 @@ func insertMany(ctx context.Context, dbPool *pgdb.Pool, qp *pgdb.QueryParams, do
 		for i := 0; i < docs.Len(); i++ {
 			doc := must.NotFail(docs.Get(i))
 
-			err := insertDocumentFallback(ctx, dbPool, qp, doc)
+			err := insertDocumentSeparately(ctx, dbPool, qp, doc)
 
 			var we *commonerrors.WriteErrors
 
@@ -126,7 +126,7 @@ func insertMany(ctx context.Context, dbPool *pgdb.Pool, qp *pgdb.QueryParams, do
 	return int32(docs.Len()), &insErrors
 }
 
-// insertDocument prepares and executes actual INSERT request to Postgres.
+// insertDocument prepares and executes actual INSERT request to Postgres in provided transaction.
 func insertDocument(ctx context.Context, tx pgx.Tx, qp *pgdb.QueryParams, doc any) error {
 	d, ok := doc.(*types.Document)
 	if !ok {
@@ -136,19 +136,6 @@ func insertDocument(ctx context.Context, tx pgx.Tx, qp *pgdb.QueryParams, doc an
 		)
 	}
 
-	return pgdb.InsertDocument(ctx, tx, qp.DB, qp.Collection, d)
-}
-
-// insertDocument prepares and executes actual INSERT request to Postgres.
-func insertDocumentFallback(ctx context.Context, dbPool *pgdb.Pool, qp *pgdb.QueryParams, doc any) error {
-	d, ok := doc.(*types.Document)
-	if !ok {
-		return commonerrors.NewCommandErrorMsg(
-			commonerrors.ErrBadValue,
-			fmt.Sprintf("document has invalid type %s", commonparams.AliasFromType(doc)),
-		)
-	}
-
 	toInsert := d
 
 	if !toInsert.Has("_id") {
@@ -158,9 +145,7 @@ func insertDocumentFallback(ctx context.Context, dbPool *pgdb.Pool, qp *pgdb.Que
 		toInsert.Set("_id", types.NewObjectID())
 	}
 
-	err := dbPool.InTransactionRetry(ctx, func(tx pgx.Tx) error {
-		return pgdb.InsertDocument(ctx, tx, qp.DB, qp.Collection, toInsert)
-	})
+	err := pgdb.InsertDocument(ctx, tx, qp.DB, qp.Collection, toInsert)
 
 	switch {
 	case err == nil:
@@ -186,3 +171,12 @@ func insertDocumentFallback(ctx context.Context, dbPool *pgdb.Pool, qp *pgdb.Que
 		return commonerrors.CheckError(err)
 	}
 }
+
+// insertDocumentSeparately prepares and executes actual INSERT request to Postgres in separate transaction.
+//
+// It should be used in places where we don't want to rollback previous inserted documents on error.
+func insertDocumentSeparately(ctx context.Context, dbPool *pgdb.Pool, qp *pgdb.QueryParams, doc any) error {
+	return dbPool.InTransactionRetry(ctx, func(tx pgx.Tx) error {
+		return insertDocument(ctx, tx, qp, doc)
+	})
+}
diff --git a/internal/handlers/pg/msg_update.go b/internal/handlers/pg/msg_update.go
index 478784818417..8dcfde319ee7 100644
--- a/internal/handlers/pg/msg_update.go
+++ b/internal/handlers/pg/msg_update.go
@@ -97,6 +97,7 @@ func (h *Handler) MsgUpdate(ctx context.Context, msg *wire.OpMsg) (*wire.OpMsg,
 					"_id", must.NotFail(doc.Get("_id")),
 				)))
 
+				// TODO https://github.com/FerretDB/FerretDB/issues/2612
 				if err = insertDocument(ctx, tx, &qp, doc); err != nil {
 					return err
 				}
@@ -121,6 +122,7 @@ func (h *Handler) MsgUpdate(ctx context.Context, msg *wire.OpMsg) (*wire.OpMsg,
 					continue
 				}
 
+				// TODO https://github.com/FerretDB/FerretDB/issues/2612
 				rowsChanged, err := updateDocument(ctx, tx, &qp, doc)
 				if err != nil {
 					return err