explaingit

mic92/hestia

Analysis updated 2026-05-18

★ 29RustAudience · ops devopsComplexity · 3/5Setup · easy

TLDR

A build cache tool for Nix that stores past build results in GitHub's free cache storage so later CI runs can skip rebuilding unchanged parts.

Mindmap

mindmap
  root((Hestia))
    What It Does
      Cache Nix builds
      Chunk and dedupe uploads
      Garbage collect stale caches
    Tech Stack
      Rust
      Nix
      GitHub Actions
    Use Cases
      CI build caching
      Faster pipelines
      Reduced API calls
    Audience
      DevOps engineers
      Nix users

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What do people build with it?

USE CASE 1

Skip rebuilding unchanged Nix packages in CI by restoring them from GitHub's cache storage.

USE CASE 2

Reduce upload size for incremental changes using content-defined chunking instead of one blob per build item.

USE CASE 3

Avoid GitHub API rate-limit errors that competing cache tools hit on large builds.

USE CASE 4

Automatically clean up cached data for deleted branches and pull requests to stay under the 10GB cache limit.

What is it built with?

RustNixGitHub Actions

How does it compare?

mic92/hestiamatthart1983/diskwatchrestsend/flowdb
Stars292929
LanguageRustRustRust
Setup difficultyeasyeasymoderate
Complexity3/52/53/5
Audienceops devopsdeveloperdeveloper

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · easy Time to first run · 5min

Designed only for CI environments, not local developer machines, still in beta and the cache format may change before 1.0.

In plain English

Hestia is a build cache tool for projects that use Nix, a package manager that builds software in a very precise and reproducible way. The problem it solves is simple: Nix builds can be slow, and if nothing has changed, redoing them wastes time. Hestia stores the results of past builds inside GitHub's free cache storage so that later runs can skip rebuilding anything that was already done. The main reason this project exists alongside similar tools is efficiency. Instead of uploading one cache entry per built item (which can mean thousands of small uploads for a large project), Hestia packs results into a small number of large blobs. It also splits those blobs into content-defined chunks, meaning that when a project update changes only a few packages, only the changed chunks are uploaded rather than everything. This dramatically reduces upload size for incremental changes. It also avoids the rate-limiting errors that competing tools encounter on large builds because it makes far fewer API calls to GitHub. There is no account to create and no server to run. Adding two lines to a GitHub Actions workflow file is enough to start using it. The tool runs as a small background process during the CI job, intercepts Nix's build requests, serves cached results when available, and uploads new results at the end of the job. A separate optional scheduled workflow handles garbage collection, deleting cached data for branches and pull requests that no longer exist, to keep the repository within GitHub's 10 GB cache limit per repo. Hestia is designed only for continuous integration environments, not for developer machines. If a team wants shared caching that also works on local computers, the README points to other tools better suited for that. The project is currently in beta. The core behavior works and the authors consider it usable in real CI pipelines, but the cache format may still change before a stable 1.0 release, which could require clearing the cache after upgrades. The source code is written in Rust and the license is not stated in the README excerpt.

Copy-paste prompts

Prompt 1
Add Hestia to my GitHub Actions workflow to cache Nix builds in two lines.
Prompt 2
Explain how Hestia's content-defined chunking reduces upload size compared to caching per build item.
Prompt 3
Set up the scheduled garbage collection workflow for Hestia to clean up stale branch caches.
Prompt 4
Why does Hestia avoid GitHub API rate limits that other Nix cache tools run into?

Frequently asked questions

What is hestia?

A build cache tool for Nix that stores past build results in GitHub's free cache storage so later CI runs can skip rebuilding unchanged parts.

What language is hestia written in?

Mainly Rust. The stack also includes Rust, Nix, GitHub Actions.

How hard is hestia to set up?

Setup difficulty is rated easy, with roughly 5min to a first successful run.

Who is hestia for?

Mainly ops devops.

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