DynamoDB Streams — Amazon DynamoDB Streams
Change records for DynamoDB tables, read through shard iterators. One shard per stream, records are never trimmed, and a stream belongs to its table's region.
Every write to a stream-enabled table produces a change record. A stream has one shard, and its records are never trimmed.
Status: ⚠️ Partial
Quick start
export AWS_ENDPOINT_URL=http://localhost:4566
aws dynamodb update-table --table-name orders \
--stream-specification StreamEnabled=true,StreamViewType=NEW_AND_OLD_IMAGES
ARN=$(aws dynamodbstreams list-streams --query 'Streams[0].StreamArn' --output text)
SHARD=$(aws dynamodbstreams describe-stream --stream-arn "$ARN" \
--query 'StreamDescription.Shards[0].ShardId' --output text)
ITER=$(aws dynamodbstreams get-shard-iterator --stream-arn "$ARN" \
--shard-id "$SHARD" --shard-iterator-type TRIM_HORIZON \
--query ShardIterator --output text)
aws dynamodbstreams get-records --shard-iterator "$ITER"Any credentials work; with none configured, run eval "$(overcast env)" first
— see Using AWS SDKs and CLI.
What works
| Area | Behaviour |
|---|---|
| View types | KEYS_ONLY, NEW_IMAGE, OLD_IMAGE and NEW_AND_OLD_IMAGES all produce the images AWS documents |
| Iterators | TRIM_HORIZON, LATEST, AT_SEQUENCE_NUMBER and AFTER_SEQUENCE_NUMBER |
| Consumers | Lambda event source mappings and EventBridge Pipes poll table streams |
| Regions | A stream belongs to its table’s region, and every record carries awsRegion |
| Protocols | AWS JSON 1.0 on the shared root endpoint, and Smithy RPC v2 CBOR |
Differences from AWS
| Area | On AWS | Overcast |
|---|---|---|
| Shards | Split as throughput grows, with parent/child lineage | One per stream, its id derived from the table name and never rolling over, so splitting and traversal cannot be exercised |
| Trimming | Records are discarded after 24 hours | Records survive for the life of the table, so TRIM_HORIZON always replays from the first write |
| Region-scoped ARNs | A regional endpoint refuses another region’s stream ARN | DescribeStream and GetShardIterator answer ResourceNotFoundException the same way |
| Cross-region triggers | Streams and their consumers are region-scoped | A Lambda event source mapping or pipe naming one region’s stream is not fired by writes to a same-named table in another region |
Operations
All 4 listed operations are implemented. Per-operation status, notes and AWS API links: DynamoDB Streams operations.
Related
- DynamoDB — where streams are enabled
- Kinesis Data Streams
- All service pages
- Service names and state overrides
- AWS API reference