diff --git a/server/src/main/java/org/apache/druid/segment/metadata/CoordinatorSegmentMetadataCache.java b/server/src/main/java/org/apache/druid/segment/metadata/CoordinatorSegmentMetadataCache.java
index 49254c1da5c..bfc7784caf3 100644
--- a/server/src/main/java/org/apache/druid/segment/metadata/CoordinatorSegmentMetadataCache.java
+++ b/server/src/main/java/org/apache/druid/segment/metadata/CoordinatorSegmentMetadataCache.java
@@ -811,16 +811,14 @@ public class CoordinatorSegmentMetadataCache extends AbstractSegmentMetadataCach
         mergedColumnTypes.put(column, columnType);
       }
 
-      Map<String, ColumnType> columnMapping = segmentSchema.getColumnTypeMap();
+      final Map<String, ColumnType> columnMapping = segmentSchema.getColumnTypeMap();
 
       // column type to be updated is not present in the existing schema
-      boolean missingUpdateColumns = false;
-      // new column to be added is already present in the existing schema
-      boolean existingNewColumns = false;
+      final Set<String> missingUpdateColumns = new HashSet<>();
 
       for (String column : segmentSchema.getUpdatedColumns()) {
         if (!mergedColumnTypes.containsKey(column)) {
-          missingUpdateColumns = true;
+          missingUpdateColumns.add(column);
           mergedColumnTypes.put(column, columnMapping.get(column));
         } else {
           mergedColumnTypes.compute(column, (c, existingType) -> columnTypeMergePolicy.merge(existingType, columnMapping.get(column)));
@@ -829,23 +827,24 @@ public class CoordinatorSegmentMetadataCache extends AbstractSegmentMetadataCach
 
       for (String column : segmentSchema.getNewColumns()) {
         if (mergedColumnTypes.containsKey(column)) {
-          existingNewColumns = true;
           mergedColumnTypes.compute(column, (c, existingType) -> columnTypeMergePolicy.merge(existingType, columnMapping.get(column)));
         } else {
           mergedColumnTypes.put(column, columnMapping.get(column));
         }
       }
 
-      if (missingUpdateColumns || existingNewColumns) {
+      if (!missingUpdateColumns.isEmpty()) {
         log.makeAlert(
-            "Error merging delta schema update with existing row signature. segmentId [%s], "
-            + "existingSignature [%s], deltaSchema [%s], missingUpdateColumns [%s], existingNewColumns [%s].",
-            segmentId,
-            existingSignature,
-            segmentSchema,
-            missingUpdateColumns,
-            existingNewColumns
-        ).emit();
+               "Datasource schema mismatch detected. The delta realtime segment schema contains columns "
+               + "that are not defined in the datasource schema. "
+               + "This indicates a potential issue with schema updates on the Coordinator. "
+               + "Please review relevant Coordinator metrics and logs for task communication to identify any issues."
+           )
+           .addData("datasource", segmentId.getDataSource())
+           .addData("existingSignature", existingSignature)
+           .addData("deltaSchema", segmentSchema)
+           .addData("missingUpdateColumns", missingUpdateColumns)
+           .emit();
       }
 
       mergedColumnTypes.forEach(builder::add);