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Differences from DynamoDB

This document lists all known behavioral differences between ExtendDB and real Amazon DynamoDB. Use it to understand what works identically and what requires adaptation when switching between ExtendDB and the real service.

Storage and Infrastructure

Area DynamoDB ExtendDB
Storage backend Proprietary distributed storage PostgreSQL
Global Tables CreateGlobalTable, replication Not implemented (returns UnknownOperationException)
DAX (Accelerator) In-memory caching layer Not applicable
PartiQL ExecuteStatement, BatchExecuteStatement Not implemented (returns UnknownOperationException)

Authentication and Authorization (AWS IAM/STS auth surface used by DynamoDB)

Area DynamoDB ExtendDB
Credential management AWS IAM console/API extenddb manage CLI and /management REST API
Access key prefixes AKIA (long-term), ASIA (session) AWS-wide IAM/STS conventions AKIAEXTENDDB (long-term), ASIAEXTENDDB (session)
Federated roles AssumeRoleWithSAML, AssumeRoleWithWebIdentity Not implemented
Role chaining Supported Not implemented
SourceIdentity, TransitiveTagKeys Supported Not implemented
Resource policies Supported Not implemented (deferred)

Import and Export

Area DynamoDB ExtendDB
Import source S3BucketSource (S3 bucket) FileSource (local filesystem path)
Export destination S3 bucket Local filesystem path
Import formats CSV, DYNAMODB_JSON, ION CSV, DYNAMODB_JSON, ION
Export formats DYNAMODB_JSON, ION DYNAMODB_JSON, ION
Import execution Asynchronous (background job) Synchronous (completes before returning)
Export execution Point-in-time snapshot Current snapshot, synchronous

Control Plane

Area DynamoDB ExtendDB
Table creation delay Returns CREATING immediately; transitions to ACTIVE typically within seconds. Same behavior for on-demand and provisioned Configurable via control_plane_delay_seconds runtime setting (default: 5s)
DeletionProtectionEnabled Enforced Enforced (accepted and stored, DeleteTable rejects when enabled)

Time to Live (TTL)

Area DynamoDB ExtendDB
TTL attribute name Any UTF-8 string (1–255 bytes) Restricted to [a-zA-Z0-9._-]+ (1–255 bytes). Names with spaces, quotes, or other special characters are rejected. This eliminates SQL injection risk in the TTL expression index.
TTL deletion Background process, items deleted within 48 hours of expiry Background worker with indexed sweep, configurable target via ttl_deletion_target_seconds (default: 300s)
TTL stream records REMOVE events with userIdentity: {type: "Service", principalId: "dynamodb.amazonaws.com"} Supported — TTL deletions generate REMOVE stream records with the same userIdentity
TTL modification cooldown Enforces a cooldown period between enable/disable changes ("Time to live has been modified multiple times within a fixed interval") No cooldown — TTL can be enabled and disabled immediately. Intentional divergence for faster local development.

Tagging

Area DynamoDB ExtendDB
TagResource / UntagResource Validates resource ARN exists, returns ResourceNotFoundException for missing tables Matches DynamoDB — validates resource ARN and returns ResourceNotFoundException for missing tables.

Secondary Indexes

Area DynamoDB ExtendDB
GSI update propagation Eventually consistent (milliseconds to seconds) Per-GSI propagation delay. System default: gsi_propagation_delay_ms setting (default 10ms). Each GSI can override with its own propagation_delay_ms (stored in catalog). A value of 0 means synchronous (future sync GSI feature).
Multi-part base table keys Not supported Preview extension (opt-in via enable_multipart_keys setting). Standard single/composite keys work identically.

Capacity and Throttling

Area DynamoDB ExtendDB
Provisioned throughput Token bucket per table/partition Token bucket per table/partition, matching DynamoDB's burst and refill behavior
On-demand capacity Automatic scaling Fixed initial burst capacity (4000 WCU / 12000 RCU), no auto-scaling
Throttling Always on; throttles requests that exceed provisioned/burst capacity. No setting to disable Configurable via throttling_enabled runtime setting (default: true)

Operations Not Implemented

The following operations return UnknownOperationException:

  • CreateGlobalTable, DescribeGlobalTable, ListGlobalTables, UpdateGlobalTable
  • DescribeGlobalTableSettings, UpdateGlobalTableSettings
  • ExecuteStatement, BatchExecuteStatement, ExecuteTransaction
  • DescribeContributorInsights, UpdateContributorInsights
  • DescribeKinesisStreamingDestination, EnableKinesisStreamingDestination, DisableKinesisStreamingDestination
  • DescribeTableReplicaAutoScaling, UpdateTableReplicaAutoScaling

Runtime Configuration

ExtendDB exposes runtime settings that have no DynamoDB equivalent:

Setting Default Description
control_plane_delay_seconds 5 Simulated delay for table state transitions (CREATING → ACTIVE, DELETING → removed)
gsi_propagation_delay_ms 10 System-wide default GSI propagation delay (milliseconds). Per-GSI overrides stored in catalog. 0 = synchronous.
throttling_enabled true Enable provisioned capacity throttling (token bucket per table/partition)
enable_multipart_keys false Enable multi-part base table key extension
log_level info Runtime log level (trace, debug, info, warn, error)
sqlx_log_level warn Separate log level for sqlx query traces
allow_credential_import true Allow importing credentials via the management API

Web Console

ExtendDB includes a built-in web management console at /console for credential and account management. DynamoDB uses the AWS Management Console.

License

Copyright 2026 ExtendDB contributors. Licensed under the Apache License, Version 2.0. See LICENSE for the full text.

This software is provided "as is" without warranty of any kind. ExtendDB is not affiliated with, endorsed by, or sponsored by Amazon Web Services. "DynamoDB" is a trademark of Amazon.com, Inc.