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dgraph-io/ristretto

A fast, concurrent, memory-bound cache library for Go with cost-based eviction and TinyLFU admission.

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What is it?

Ristretto is an in-memory cache library for Go, built for workloads where many goroutines read and write the same cache and contention would otherwise become a bottleneck. It was created to serve as a contention-free cache inside Dgraph.

Eviction uses a SampledLFU policy and admission uses TinyLFU, which together aim for high hit ratios while keeping memory overhead small (about 12 bits per frequency counter). Each item carries a user-defined cost, so a large, valuable item can evict several smaller ones instead of counting as a single entry. Cache size is bounded by total cost rather than item count.

The API is small: configure NumCounters, MaxCost and BufferItems, then call Set, Get and Del. Optional metrics expose throughput and hit ratio statistics. Ristretto is a single-process library and is not distributed. It requires Go 1.21 or later, and the v2 module uses generics.

Key features

  • 01Cost-based eviction, so large valuable items can displace several smaller ones.
  • 02SampledLFU eviction paired with TinyLFU admission for high hit ratios.
  • 03Safe for use from many goroutines concurrently.
  • 04Optional metrics for throughput and hit ratio.
  • 05Generic v2 API with Config[K, V] type parameters.

Use cases

  • Caching computed results or database rows inside a Go service to reduce repeated work.
  • Bounding cache memory by total item cost rather than entry count.
  • Building embedded storage engines or databases that need an in-process cache, as Badger and Dgraph do.

Quick start

  1. 1

    Install Go 1.21 or above

  2. 2

    Add Ristretto to your project with go get

    go get github.com/dgraph-io/ristretto/v2

Things to know

  • The v1 API is older; v2 uses generics and has a slightly different interface, so existing code may need changes.
  • Set calls for new items are not guaranteed to be stored, since they can be dropped under contention or by the admission policy.

Topics

#cache#go#golang#in-memory#concurrency#performance#lfu#library

FAQ

What is ristretto?
A fast, concurrent, memory-bound cache library for Go with cost-based eviction and TinyLFU admission. Ristretto is an in-memory cache library for Go, built for workloads where many goroutines read and write the same cache and contention would otherwise become a bottleneck. It was created to serve as a contention-free cache inside Dgraph.
Is ristretto free to use? What license does it have?
ristretto is open source under the Apache-2.0 license. Check the license terms before using it in commercial products.
Is ristretto still maintained?
Updated within 6 months. The last commit to ristretto was on Sep 21, 2026.
What can I use ristretto for?
Caching computed results or database rows inside a Go service to reduce repeated work. Bounding cache memory by total item cost rather than entry count. Building embedded storage engines or databases that need an in-process cache, as Badger and Dgraph do.
How do I install ristretto?
Install Go 1.21 or above Add Ristretto to your project with go get: go get github.com/dgraph-io/ristretto/v2
Where can I get ristretto?
The source code and installation instructions are on GitHub: https://github.com/dgraph-io/ristretto

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