Vector Databases

Annoy

Efficient Approximate Nearest Neighbors implementation in C++ with Node bindings.

Status
Generally available
Last checked
Checked · Oct 13, 2026
License
Open source
Pricing
Free tier
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What it is

Annoy is a library designed for performing Approximate Nearest Neighbors (ANN) search, optimized for memory usage and efficient loading/saving to disk. Written in C++, it provides bindings for Node.js, allowing integration into JavaScript environments. Annoy is particularly suited for applications requiring fast and scalable similarity searches, such as recommendation systems or clustering tasks. It supports multiple languages including Python, Golang, and Lua, making it versatile for various development environments.

Combines efficient memory usage with multi-language support for ANN.

When it fits — and when it doesn’t

A good fit for

  • Building recommendation systems

    Efficiently handles similarity searches needed for recommendations.

  • Applications with memory constraints

    Optimized for low memory usage, suitable for resource-limited environments.

Look elsewhere if

  • Real-time data processing

    Approximate methods may not meet real-time precision requirements.

  • Projects requiring frequent updates

    Lack of recent updates may hinder progress on cutting-edge features.

Known weaknesses

Each one links to the public issue, changelog or docs page it came from, where we have one.

  1. 01

    No recent updates

    Last commit was in 2025.

  2. 02

    Low Node.js adoption

    Weekly downloads are zero.

  3. 03

    High open issues count

    86 open issues on GitHub.

What it does well

  • Memory optimization

    Optimized for memory usage and efficient loading/saving to disk.

  • Multi-language support

    Supports C++, Python, Golang, and Lua.

  • Open source

    Licensed under MIT and Apache-2.0.

Pricing

Free tier
Yes
Paid from
—
Model
Flat rate
Enterprise plan
No

Pricing last confirmed Sep 28, 2026.

Performance benchmarks

How Fast Is It?

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Setup steps, common gotchas and what to check after 30 days.

Open the setup guide →
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