Differences from DynamoDB

May 19, 2026 · View on GitHub

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

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.