---
title: "HeliosDB-Lite Documentation"
description: "HeliosDB Lite documentation: an embeddable PostgreSQL-compatible database with vector search, time travel, branching and row-level security."
---

# HeliosDB-Lite Documentation

**High-performance embedded database with vector search, time-travel queries, and Git-like branching**

[![Rust](https://img.shields.io/badge/rust-1.70+-orange.svg)](https://www.rust-lang.org/)
[![License](https://img.shields.io/badge/license-SSPL--1.0-orange.svg)](https://www.mongodb.com/legal/licensing/server-side-public-license)

---

## What is HeliosDB-Lite?

HeliosDB-Lite is a lightweight, embeddable database engine written in Rust that combines the simplicity of SQLite with advanced features typically found in enterprise databases:

- **PostgreSQL-Compatible SQL** - Standard SQL syntax with 95%+ PostgreSQL compatibility
- **Vector Search** - Built-in HNSW indexing for similarity search and AI/ML applications
- **Database Branching** - Git-like branching for development, testing, and experimentation
- **Time-Travel Queries** - Query historical data at any point in time
- **Materialized Views** - Automatic and incremental view refresh
- **Multi-Tenancy** - Row-level security and tenant isolation

## Quick Start

### Installation

HeliosDB-Lite is source-available under SSPL-1.0 and is distributed to
licensed customers. It is **not** published on crates.io, PyPI, npm, Docker
Hub or Homebrew. To get access, contact
[sales@heliosdb.com](mailto:sales@heliosdb.com).

With the source distribution unpacked, build the server / REPL binary:

```bash
cd heliosdb-lite
cargo build --release
export PATH="$PWD/target/release:$PATH"
```

From Python, Node.js, Go and other languages, connect to a running Lite server
with any PostgreSQL driver, or with the Apache-2.0 client SDKs in
[HeliosDatabase/HeliosDB-SDKs](https://github.com/HeliosDatabase/HeliosDB-SDKs)
(see [SDKs & Integrations](https://www.heliosdb.com/docs/lite/api/sdks/)).

### Try the REPL

```bash
# Start interactive shell
heliosdb-lite repl --data-dir ./mydb

# Or in-memory mode
heliosdb-lite repl --memory
```

```sql
CREATE TABLE users (id INT PRIMARY KEY, name TEXT);
INSERT INTO users VALUES (1, 'Alice');
SELECT * FROM users;
```

### Run the Server

```bash
# The server refuses to start without a REST token-signing secret
export HELIOSDB_JWT_SECRET="$(openssl rand -hex 32)"
heliosdb-lite start --data-dir ./mydb      # PostgreSQL wire on 127.0.0.1:5432, REST on 8080

psql -h 127.0.0.1 -p 5432 -U postgres
```

## Key Features

- **[Database Branching](https://www.heliosdb.com/docs/lite/features/branching/)**: create isolated branches for development, testing, or experimentation without duplicating data.
- **[Time-Travel Queries](https://www.heliosdb.com/docs/lite/features/time-travel/)**: query data as it existed at any point in time using `AS OF TIMESTAMP` syntax.
- **[Vector Search](https://www.heliosdb.com/docs/lite/features/vector-search/)**: built-in HNSW vector indexing for similarity search, RAG applications, and embeddings.
- **[Materialized Views](https://www.heliosdb.com/docs/lite/features/materialized-views/)**: stored query results refreshed in full, concurrently or incrementally; automatic background refresh is planned.

## Deployment Options

| Mode | Description | Best For |
|------|-------------|----------|
| **Embedded** | In-process engine (licensed source distribution) | Applications, edge devices, testing |
| **Server** | PostgreSQL-compatible server | Multi-client access, production |
| **In-Memory** | RAM-only storage | Testing, caching, ephemeral data |

## Documentation Sections

- **[Getting Started](https://www.heliosdb.com/docs/lite/getting-started/)** - Installation, quick start, deployment
- **[User Guide](https://www.heliosdb.com/docs/lite/user-guide/sql-reference/)** - SQL reference, REPL commands, configuration
- **[Features](https://www.heliosdb.com/docs/lite/features/)** - Branching, time-travel, vectors, security
- **[API Reference](https://www.heliosdb.com/docs/lite/api/rest-api/)** - REST API and the Python, TypeScript and Go SDKs
- **[Releases](https://www.heliosdb.com/docs/lite/releases/changelog/)** - Changelog and release notes

---

**Need help?** Check the [FAQ](https://www.heliosdb.com/docs/lite/resources/faq/) or contact support@heliosdb.com.