diff --git a/internal/types/types.go b/internal/types/types.go
index 73387bdd1cc1a09fd6d6a360ea7d409c7ac1a580..a2c2ae170f406c9e43c54cee6d7e4078bd77727c 100644
--- a/internal/types/types.go
+++ b/internal/types/types.go
@@ -192,6 +192,19 @@ type DataCoord interface {
 	// response struct `GetRecoveryInfoResponse` contains the list of segments info and corresponding vchannel info
 	// error is returned only when some communication issue occurs
 	GetRecoveryInfo(ctx context.Context, req *datapb.GetRecoveryInfoRequest) (*datapb.GetRecoveryInfoResponse, error)
+
+	// SaveBinlogPaths updates segments binlogs(including insert binlogs, stats logs and delta logs)
+	//  and related message stream positions
+	//
+	// ctx is the context to control request deadline and cancellation
+	// req contains the collection/partition id to query
+	//
+	// response status contains the status/error code and failing reason if any
+	// error is returned only when some communication issue occurs
+	//
+	// there is a constraint that the `SaveBinlogPaths` requests of same segment shall be passed in sequence
+	// 	the root reason is each `SaveBinlogPaths` will overwrite the checkpoint position
+	//  if the constraint is broken, the checkpoint position will not be monotonically increasing and the integrity will be compromised
 	SaveBinlogPaths(ctx context.Context, req *datapb.SaveBinlogPathsRequest) (*commonpb.Status, error)
 	GetFlushedSegments(ctx context.Context, req *datapb.GetFlushedSegmentsRequest) (*datapb.GetFlushedSegmentsResponse, error)