@elizaos/plugin-inmemorydb

A pure in-memory, ephemeral database adapter for elizaOS. All data is completely lost on process restart or when close() is called.

Features

- Zero Configuration: No database setup required - just works out of the box
- Zero Persistence: Data is never written to disk or localStorage
- Completely Ephemeral: All data is lost when the process ends
- Cross-Platform: Works identically in Node.js and browsers
- Vector Search: Built-in HNSW index for semantic similarity search (also ephemeral)
- Same Interface: Implements the standard IDatabaseAdapter interface

When to Use

This plugin is ideal for:

- ✅ Testing and CI/CD: Perfect for tests that need a fresh database each run
- ✅ Stateless deployments: When you want agents to start fresh each time
- ✅ Development: Quick prototyping without persistence overhead
- ✅ Privacy-focused applications: When data should never be stored
- ✅ Demos and examples: Clean slate for each demonstration

Not recommended for:

- ❌ Production systems that need data persistence
- ❌ Long-running agents that need to remember past interactions
- ❌ Multi-process deployments (data is not shared between processes)

Installation

``bash
bun add @elizaos/plugin-inmemorydb
`

Quick Start

$3

`typescript
import { plugin } from "@elizaos/plugin-inmemorydb";

// Add to your agent configuration
const agent = {
plugins: [plugin],
// ...
};
`

$3

`typescript
import { plugin } from "@elizaos/plugin-inmemorydb";

// Add to your agent configuration
const agent = {
plugins: [plugin],
// ...
};
`

API

$3

`typescript
import {
InMemoryDatabaseAdapter,
MemoryStorage,
} from "@elizaos/plugin-inmemorydb";

const storage = new MemoryStorage();
const adapter = new InMemoryDatabaseAdapter(storage, agentId);
await adapter.init();

// Use the adapter...

// When done, close to clear all data
await adapter.close();
`

$3

`typescript
// Clear all data (adapter still usable)
await storage.clear();

// Or close the adapter entirely (also clears data)
await adapter.close();
`

Comparison with Other Database Plugins

| Feature | plugin-inmemorydb | plugin-localdb | plugin-sql |
| --------------- | ------------------ | ------------------ | ------------------- |
| Persistence | None (ephemeral) | JSON files | PostgreSQL |
| Setup | Zero configuration | Zero configuration | Requires PostgreSQL |
| Data on restart | Lost | Preserved | Preserved |
| Best for | Testing/dev | Local dev | Production |

How It Works

The plugin uses simple JavaScript Map data structures to store all data:

`
Memory
├── Collections (Map>)
│ ├── agents: Map
│ ├── memories: Map
│ ├── rooms: Map
│ └── ... (other collections)
└── HNSW Vector Index (in-memory)
`

When the process ends or close()` is called, all Maps are cleared and data is gone forever.

Vector Search

The plugin includes an ephemeral HNSW (Hierarchical Navigable Small World) implementation for vector similarity search:

- Semantic memory search
- Similar content retrieval
- Embedding-based queries

The vector index is also purely in-memory and is cleared with all other data.

License

MIT