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Streams: a request without StreamArn, ShardId or ShardIterator answers SerializationException; DynamoDB Streams answers ValidationException #757
Description
DynamoDB Streams answers a request that lacks a required member with 400 ValidationException. ExtendDB answers it with 400 SerializationException, because the request does not deserialize into the input type.
Measured on Amazon DynamoDB Streams in us-east-1 on 2026-10-29 with raw signed requests, so no SDK check ran first. ExtendDB is main at 8099ff0 with the same requests:
| Request | DynamoDB Streams | ExtendDB |
|---|---|---|
DescribeStream with body {} |
ValidationException: Invalid StreamArn |
SerializationException: missing field `StreamArn` |
GetShardIterator without ShardId |
ValidationException: 1 validation error detected: Value at 'shardId' failed to satisfy constraint: Member must not be null |
SerializationException: missing field `ShardId` |
GetRecords with body {} |
ValidationException: Invalid ShardIterator: Missing ShardIterator |
SerializationException: missing field `ShardIterator` |
The service's type is com.amazon.coral.validate#ValidationException. ExtendDB's is com.amazon.coral.service#SerializationException.
Why it matters
SDKs surface the error code. A client or a test that expects ValidationException for a Streams request with a missing member gets SerializationException from ExtendDB, and a match on the service's message fails.
Proposed change
Make StreamArn, ShardId and ShardIterator optional in the Streams input types and refuse a missing value in the handler with the messages above. A StreamArn that is present but not a stream ARN is refused with Invalid StreamArn by open pull request #466, which also closes #450 and #451.
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