Dynoxide

A DynamoDB emulator in Rust, backed by SQLite. Runs as an HTTP server or an MCP server for coding agents, embeds into Rust and iOS applications as a library, and compiles to WebAssembly for the browser.

Why Dynoxide?

I built Dynoxide because DynamoDB Local is slow, heavy, and can't embed. It needs a JVM, and the typical Docker-based setups adds 2–3 seconds of cold-start, ~193 MB of memory at idle, and a ~225MB Docker image (~473 MB on disk) before you've done anything useful. If you're running integration tests, that's Docker starting, the JVM warming up, and your pipeline waiting.

Dynoxide is a native binary. It starts in milliseconds, idles at ~5.0 MB, and ships as a ~3 MB download. Point any DynamoDB SDK at it and your tests just work.

For Rust projects, there's also an embedded mode - direct API calls via Database::memory() with no HTTP layer at all. Each test gets an isolated in-memory database with zero startup cost. And because it compiles to a native library with no runtime dependencies, it runs on platforms where DynamoDB Local can't, including iOS.

Performance

Local Development (Apple Silicon)

CI (GitHub Actions)

Numbers from ubuntu-latest (4-core AMD EPYC 9V74, 16GB RAM). Commit 54a2cb6.

The gap is wider on Apple Silicon because the faster CPU amplifies the difference between native code and JVM overhead. Both are real measurements of the same benchmark suite. Full methodology and per-operation breakdowns →

Conformance

Dynoxide is continuously verified against real DynamoDB by Parity Suite, the DynamoDB conformance suite that runs one test matrix against AWS itself and every major DynamoDB emulator. Pass rates move as the suite grows and each engine changes, so rather than pin a snapshot that goes stale, see the live standings:

• Live standings: current pass rates for every engine, broken down by tier
• paritysuite/dynamodb-conformance: the suite itself, the raw results, and how each target is run

Disclosure: Dynoxide and Parity Suite are maintained by the same person. The suite scores Dynoxide on the same public matrix it runs against every other engine, and the results and test code are open.

This covers the native build. The WebAssembly build is scored as its own row: it passes every test it implements, with a far higher skip count than any other target because several operations are still missing.

How It Compares

LocalStack uses DynamoDB Local internally as its DynamoDB engine, so its startup and memory overhead includes DynamoDB Local's JVM plus LocalStack's own Python routing layer.

Quick Start

Install from npm and start a local server:

npm install --save-dev dynoxide
npx dynoxide --port 8000

Or run it in Docker, a drop-in for amazon/dynamodb-local:

docker run --rm -p 8000:8000 ghcr.io/nubo-db/dynoxide

Point any AWS SDK or DynamoDB client at http://localhost:8000. For Homebrew, Cargo, pre-built binaries, and embedding as a Rust library, see the installation guide.

Documentation

• Installation - npm, Homebrew, Cargo, binaries, GitHub Actions, and Docker
• HTTP server - running the DynamoDB-compatible HTTP API
• Testcontainers - driving the container from a test suite, and the wait strategy it needs
• MCP server - the Model Context Protocol server for coding agents
• DynamoDB Streams - enabling and reading stream records
• Import CLI - loading data, table filtering, and anonymisation
• WebAssembly - the browser build and embed contract
• Using as a Rust library - embedded mode and feature flags
• Compatibility - operation, expression, and PartiQL coverage versus DynamoDB
• Versioning - what the version number promises and what forces a major
• Releasing - release cadence and process

Supported Operations

Dynoxide implements the DynamoDB API across tables, items, query and scan, batches, transactions, PartiQL, streams, TTL, and tags, with GSI and LSI support, the full expression syntax, and DynamoDB-compatible pagination, validation, and error codes. For the operation-by-operation breakdown and a comparison, see the compatibility summary.

Limitations

Dynoxide is built for local development, testing, and CI, not as a production DynamoDB replacement, so two classes of thing are missing on purpose.

Cloud-only operations with no local equivalent aren't implemented: backups and point-in-time restore, global tables, Kinesis streaming, resource policies, and capacity management. Call one and you get an UnknownOperationException.