AWS Open-Sources ExtendDB, a DynamoDB-Compatible Adapter That Runs on PostgreSQL and Cassandra
AWS released ExtendDB v0.1 on May 20, an Apache 2.0 adapter implementing the DynamoDB wire protocol on pluggable backends including PostgreSQL and Apache Cassandra, targeting local dev, CI/CD, on-premises, and hybrid environments.
Overview
Amazon Web Services on May 20 released ExtendDB, an open source project that implements the Amazon DynamoDB API with pluggable storage backends, enabling teams to run DynamoDB-shaped workloads outside of AWS — on developer laptops, in CI/CD pipelines, on-premises, and across hybrid or disconnected environments, according to the AWS Database Blog. The project is released under the Apache 2.0 license and available at github.com/ExtendDB/extenddb.
What We Know
ExtendDB’s core design is straightforward: it is, as the AWS Database Blog describes it, “a translator sitting between your application and your storage backend.” It implements the DynamoDB wire protocol, meaning that any AWS SDK, CLI, or tool that already targets DynamoDB works against ExtendDB with only an endpoint URL change — no application code modifications required.
The reference storage backend at launch is PostgreSQL. The AWS What’s New announcement describes the architecture as one where “the pluggable architecture allows the community to add new storage backends.” The project ships with PostgreSQL as its first backend, and according to the AWS Database Blog, “additional backends like Apache Cassandra for horizontal scale can be implemented without modifying the core.” The ExtendDB project website lists the Cassandra backend as supported via the pluggable interface, alongside community-contributed backends.
The API coverage is broad. ExtendDB implements the DynamoDB control plane (CreateTable, DeleteTable, DescribeTable, ListTables, UpdateTable) and data plane (PutItem, GetItem, DeleteItem, UpdateItem with conditional expressions, Query, Scan, BatchGetItem, BatchWriteItem, TransactGetItems, TransactWriteItems), as well as Streams, TTL, Import/Export, and resource tagging, per the AWS Database Blog.
Security is built in from the start. The AWS Database Blog states that “TLS is mandatory and auto-generates a self-signed certificate on first run. SigV4 authentication with a local IAM-like credential store means your application code uses the same signing logic it uses against the DynamoDB service.”
The project is written in Rust and requires Rust 1.85+ and PostgreSQL 14+, as noted in the AWS Database Blog.
AWS has been explicit about the current release’s intended scope. As the AWS Database Blog states: “This is a v0.1 release for development, testing, and experimentation.” The release is aimed at three primary scenarios: local development and CI/CD; on-premises and air-gapped environments; and multi-cloud and hybrid deployments.
AWS distinguishes ExtendDB from the existing DynamoDB Local tool. The AWS Database Blog notes: “DynamoDB Local is a single-process tool intended for unit testing. ExtendDB targets a broader set of local development and on-premises scenarios as an early-stage project.”
The blog post was authored by Lee Hannigan, described as a Senior Amazon DynamoDB Database Engineer based in Donegal, Ireland, and Deepthi Mohan, Principal Product Manager in the DynamoDB team, according to the AWS Database Blog.
What We Don’t Know
Pricing for a potential commercial or managed version of ExtendDB has not been announced. The ExtendDB project website notes that ExtendDB does not replicate managed-service features: global tables, auto-scaling, backup and restore, and DAX are not supported in a self-hosted deployment. A roadmap file exists in the repository but AWS has not detailed which features or additional backends are planned for future releases. It is also not clear when or whether a stable v1.0 release is targeted.
The project had accumulated 314 stars and 22 forks on GitHub as of late May 2026, reflecting early-stage community interest.
Analysis
ExtendDB represents a meaningful shift in how AWS frames DynamoDB’s reach. DynamoDB has historically been a cloud-bound managed service — teams building DynamoDB-native applications have relied on DynamoDB Local for unit tests or simply accepted the cloud-only constraint. By releasing ExtendDB with a pluggable backend design, AWS is positioning DynamoDB’s API as a portable programming model rather than a cloud-tethered service.
The choice of PostgreSQL as the reference backend is pragmatic: it is widely available in every environment where ExtendDB is intended to run. The addition of an Apache Cassandra backend path addresses the horizontal scaling requirement that PostgreSQL alone cannot cover. The Rust implementation signals performance and safety priorities consistent with the broader direction AWS has taken across its infrastructure tooling.
For developers building applications against DynamoDB, the practical benefit is a high-fidelity local development loop without cloud connectivity or an AWS account. For platform and infrastructure teams, ExtendDB opens a door to running DynamoDB-shaped workloads in on-premises data centers or at the edge — territory where the fully managed service cannot reach.