Error: DynamoDB BatchSave not working

Legacy Java DynamoDBMapper.batchSave does not guarantee that all requested items were persisted. Inspect its returned failed batches and exceptions. Batch saves also replace item contents, so they are not a substitute for partial UpdateItem operations or conditional writes.

1. Check each model’s table mapping, partition key, optional sort key, and converters. Validate request sizes and duplicate keys.
2. Inspect FailedBatch results and retry only unfinished work with bounded backoff. Do not ignore a nonempty failure list.
3. Verify permissions for the underlying BatchWriteItem operation and inspect throttling on tables and GSIs.
4. If the application needs optimistic locking, per-item conditions, or atomicity across items, choose individual conditional operations or a transaction.

DynamoDBMapper belongs to the unsupported Java SDK 1.x line. With Java 2.x, use DynamoDbEnhancedClient.batchWriteItem and WriteBatch definitions. Check the BatchWriteResult methods unprocessedPutItemsForTable and unprocessedDeleteItemsForTable and resubmit those operations. Each service request is still limited to 25 puts or deletes.

See Java mapping and migration and AWS documentation.