DynamoDB

Overview

DevCloud DynamoDB uses BadgerDB as its embedded key-value storage backend. Table metadata is kept in an in-memory index (protected by RWMutex), while items are persisted in BadgerDB with composite keys (_item/{table}#{partitionKey}#{sortKey}).

Supported attribute types: S (String), N (Number), B (Binary), BOOL, NULL, L (List), M (Map).

Supported APIs

Operation	Description
CreateTable	Create table with partition key (HASH) and optional sort key (RANGE)
DeleteTable	Delete table and all its items
ListTables	List all table names
PutItem	Insert or overwrite an item
GetItem	Retrieve an item by primary key
DeleteItem	Delete an item by primary key
Query	Query items by partition key
Scan	Full table scan

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

No UpdateItem (use PutItem to overwrite entire item)
No batch operations (BatchGetItem, BatchWriteItem)
No transactions (TransactGetItems, TransactWriteItems)
No secondary indexes (GSI/LSI)
No DynamoDB Streams
No advanced filter expressions on Query/Scan
No projection expressions
No conditional writes (ConditionExpression)
No TTL