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DynamoDB

Overview

DevCloud DynamoDB persists tables and items in SQLite (dynamodb.db under the service's data_dir), with table metadata also held in an in-memory index guarded by an RWMutex.

All ten AttributeValue types are supported: S, N, B, BOOL, NULL, L (List), M (Map), and the SS / NS / BS sets.

Supported APIs

These 20 operations are hand-verified — implemented by the provider, not by the CRUD engine. Everything else DynamoDB models is served at a lower tier or not at all; fidelity-manifest.md is the per-operation answer.

Operation Description
CreateTable Create table with partition key (HASH), optional sort key (RANGE), GSIs, LSIs and a StreamSpecification
UpdateTable / DescribeTable / DeleteTable / ListTables Manage and inspect tables
PutItem Insert or overwrite an item; honours ConditionExpression
GetItem Retrieve an item by primary key; honours ProjectionExpression
UpdateItem Apply an UpdateExpression to one item
DeleteItem Delete an item by primary key; honours ConditionExpression
Query Query by partition key, against the table or a named IndexName; honours FilterExpression
Scan Full table scan; honours FilterExpression
BatchGetItem / BatchWriteItem Multi-item reads and writes
TransactGetItems / TransactWriteItems Transactional reads and writes
UpdateTimeToLive / DescribeTimeToLive Store and read back a table's TTL configuration
TagResource / UntagResource / ListTagsOfResource Manage table tags

Writes to a table created with StreamEnabled are published to the dynamodbstreams service, which is what makes DynamoDB Streams → Lambda event source mappings fire.

boto3 Examples

Create a table and write items

import boto3

dynamodb = boto3.client(
    "dynamodb",
    endpoint_url="http://localhost:4747",
    aws_access_key_id="test",
    aws_secret_access_key="test",
    region_name="us-east-1",
)

# Create table
dynamodb.create_table(
    TableName="users",
    KeySchema=[
        {"AttributeName": "pk", "KeyType": "HASH"},
        {"AttributeName": "sk", "KeyType": "RANGE"},
    ],
    AttributeDefinitions=[
        {"AttributeName": "pk", "AttributeType": "S"},
        {"AttributeName": "sk", "AttributeType": "S"},
    ],
    BillingMode="PAY_PER_REQUEST",
)

# Put item
dynamodb.put_item(
    TableName="users",
    Item={
        "pk": {"S": "user#123"},
        "sk": {"S": "profile"},
        "name": {"S": "Alice"},
        "age": {"N": "30"},
    },
)

# Get item
response = dynamodb.get_item(
    TableName="users",
    Key={"pk": {"S": "user#123"}, "sk": {"S": "profile"}},
)
print(response["Item"])

Query and scan

# Query by partition key
response = dynamodb.query(
    TableName="users",
    KeyConditionExpression="pk = :pk",
    ExpressionAttributeValues={":pk": {"S": "user#123"}},
)
for item in response["Items"]:
    print(item)

# Full table scan
response = dynamodb.scan(TableName="users")
for item in response["Items"]:
    print(item)

AWS CLI Examples

# Create table
aws --endpoint-url http://localhost:4747 dynamodb create-table \
  --table-name my-table \
  --key-schema AttributeName=pk,KeyType=HASH \
  --attribute-definitions AttributeName=pk,AttributeType=S \
  --billing-mode PAY_PER_REQUEST

# Put item
aws --endpoint-url http://localhost:4747 dynamodb put-item \
  --table-name my-table \
  --item '{"pk": {"S": "key1"}, "data": {"S": "value1"}}'

# Get item
aws --endpoint-url http://localhost:4747 dynamodb get-item \
  --table-name my-table \
  --key '{"pk": {"S": "key1"}}'

Known Limitations

  • TTL is configuration only. UpdateTimeToLive stores the attribute name and echoes it back; nothing sweeps expired items, so a row past its TTL is still returned.
  • No pagination or capacity reporting. Responses carry no LastEvaluatedKey and no ConsumedCapacity, so Query/Scan return the whole matching set in one page and code that loops on the cursor sees one iteration.
  • No PartiQL — ExecuteStatement, ExecuteTransaction and BatchExecuteStatement are unimplemented and fail rather than answering.
  • Backups, global tables and exports answer from the CRUD engine. CreateBackup, CreateGlobalTable, DescribeContinuousBackups and their neighbours return stored, plausible shapes with no behaviour behind them — see crud-engine.md.
  • No Kinesis streaming destination (EnableKinesisStreamingDestination is unimplemented)
  • No provisioned-throughput accounting or throttling; BillingMode is recorded, never enforced
  • Single account model (account ID: 000000000000)