Cachix Blog

Cachix Deploy is Generally Available and Cachix 1.10

support@cachix.org (Domen Kožar) — Wed, 28 Jan 2026 12:00:00 +0000

After three years in beta, Cachix Deploy is now generally available.

Cachix Deploy GA

Back in July 2022, we launched Cachix Deploy in public beta. Since then, it has seen extensive usage with thousands of agents deployed - from developer laptops to production fleets.

Cachix Deploy provides continuous deployments to any Nix profile (NixOS, nix-darwin, or home-manager) using a binary cache. The architecture is simple: agents pull from your binary cache and activate new profiles, with no evaluation or building done on the target machines.

Configurable Upstream Caches

support@cachix.org (Domen Kožar) — Mon, 15 Dec 2025 08:00:00 +0000

Back in 2020, we introduced upstream caches - a feature that avoids pushing store paths already present in cache.nixos.org. At the time, we mentioned:

In the future you are going to define upstream caches within Cachix so that the typical setup of a private and public cache does not duplicate the entries between the two.

That future is now.

What’s New

The simple boolean setting has been replaced with a configurable list of upstream caches. You can now add:

Downtime due to sign up spam

support@cachix.org (Domen Kožar) — Mon, 19 Feb 2024 11:00:00 +0000

At around 2am last night, I got woken up by a PagerDuty call due to our database being unresponsive.

I immediately restarted the database and it was back up in a few minutes.

While waiting for the database to come back up, I noticed that our sign ups were being overwhelmed with spam.

The usual approach to this problem is to add a CAPTCHA. Since we’re already using a honeypot, it felt like a natural next step.

Cachix v1.7

support@cachix.org (Domen Kožar) — Fri, 12 Jan 2024 12:50:00 +0000

The v1.7 release brings two new features:

a cachix import mycache s3://mybucket command to ingest the contents of an existing S3-based binary cache into Cachix.
a standalone daemon mode that opens up a bevy of workflow improvements. Requested many times before.

External cache ingestion

The cachix import command is designed to facilitate the migration of static binary caches to Cachix. This feature is critical for users seeking to leverage Cachix’s hosted binary cache services while transitioning from their existing setups.

Stamina: Haskell library for retries

support@cachix.org (Domen Kožar) — Tue, 02 Jan 2024 15:00:00 +0000

As we deal with networking and databases in our day-to-day work, Haskell exceptions frequently arise in our code.

We’ve been using the Haskell retry package for retrying exceptions so far, but it presents several issues:

The API is cumbersome to remember, so we’ve always built a thin layer on top.
It lacks built-in support for retrying HTTP exceptions, which requires careful selection of retryable instances and adherence to the retry-after header.
To log the exception that occurred, one needs to write a logger as an exception handler.
It’s not possible to reset the retry state when a long-lived task (such as a WebSocket connection) finally succeeds.

Heavily inspired by Hynek’s Stamina for Python, we’re releasing Stamina for Haskell:

Upgraded storage plans

support@cachix.org (Domen Kožar) — Tue, 12 Sep 2023 13:00:00 +0000

We’ve recently reached a couple of milestones:

And we’re happy to announce one more milestone: upgraded storage plans for everyone!

Upgraded plans

Starter: 50 GB
Standard: 250 GB
Pro: 1500 GB

Previous plans

Starter: 20 GB
Basic: 100 GB
Pro: 1000 GB

Existing users will be upgraded to the new plans at no extra cost. Enjoy the extra space! Additionally, organizations now enjoy a free plan of 5 GB, just like regular accounts, to deepen our support for Open Source development.

Introducing Pins: Permanent Nix Binary Storage

support@cachix.org (Domen Kožar) — Tue, 23 May 2023 11:30:00 +0000

Binary caches are an indispensable ally when it comes to avoiding tedious rebuilds by distributing Nix binaries. However, caches can hoard obsolete store paths that aren’t necessary anymore, which occupy precious storage space. As the cache swells beyond its storage capacity, these old store paths eventually have to be evicted. Cachix takes care of this routinely by initiating a process known as garbage collection.

Previously, the decision of what to remove from the cache was not in the hands of the users. Store paths were cleared based on the LRU (Least Recently Used) principle. This could lead to inadvertent removal of significant files that were not accessed regularly.

Cachix 1.3: Uploads unleashed

support@cachix.org (Domen Kožar) — Wed, 08 Mar 2023 06:00:00 +0000

Serving files is the bread and butter of Cachix. Fetching store paths from Cachix is fast — downloads are served directly from fast distributed cloud storage. Uploads, however, are a different story.

Each upload still had to go directly through one of our servers, making our ingest bandwidth a scarce and highly contested resource during peak times.

Many of our users rely on Cachix in their CI pipelines, where slower uploads lead to longer CI runs and a worse developer experience, which is why we’ve been busy reorganizing our internals to remove this bottleneck.

ZSTD compression by default

support@cachix.org (Domen Kožar) — Mon, 19 Dec 2022 13:50:00 +0000

We’ve been pioneering and supporting the addition of ZSTD compression to Nix since 2018.

In November 2021, Nix 2.4 was finally released with ZSTD support.

As of today, the Cachix 1.1 client will compress any pushed binaries using zstd by default, which can be reversed back to XZ compression in the binary cache settings.

This will significantly speed up pushing, as it was previously capped at around ~3-5mbit/s due to XZ compression hitting CPU per-core limits.

Cachix Deploy Public Beta

support@cachix.org (Domen Kožar) — Fri, 29 Jul 2022 13:00:00 +0000

I’m happy to announce the public beta for Cachix Deploy.

Cachix Deploy was built to remove the hassle around managing the life cycle of a Nix profile.

Cachix Deploy provides continuous deployments to a Nix profile (like NixOS, nix-darwin or home-manager) using a binary cache.

It consists of running a simple agent process cachix deploy agent that listens for a new deployment and executes them. There’s no Nix evaluation or building done on the agent. The agent pulls all dependencies from your binary cache and activates the new profile.

NixOS OceanSprint 2021 wrap up

support@cachix.org (Domen Kožar) — Fri, 17 Dec 2021 14:30:00 +0000

Last week a dozen or so people gathered on the island of Lanzarote to hack on NixOS.

If it wasn’t for COVID-19, we’d have a week long of sauna and a private lake in Finland last year, but we had to cancel the event before it was even announced.

Wrap up

The weather on Lanzarote is usually sunny all year long.

Last week we were a bit unfortunate to have two days of wind/clouds and we still managed to hack outdoors all days!

Introducing Organizations

support@cachix.org (Domen Kožar) — Fri, 15 Oct 2021 15:30:00 +0000

Today I’m introducing Organizations support in Cachix.

If you’ve ever had to manage multiple Cachix accounts, wanted a team-specific dashboard or needed to have multiple admins, you’re going to love Organizations.

Once you’ve created an organization, it will automatically enter a 14-day trial period.

If you’d like to use Organizations for an open source project, please reach out via live chat or domen@cachix.org.

Get started

Click on “Select an account” dropdown at the top right corner:

Postmortem of outage on 20th December

support@cachix.org (Domen Kožar) — Thu, 24 Dec 2020 11:30:00 +0000

On 20 December, Cachix experienced a six-hour downtime, the second significant outage since the service started operating on 1 June 2018.

Here are the details of what exactly happened and what has been done to prevent similar events from happening.

Timeline (UTC)

02:55:07 - Backend starts to emit errors for all HTTP requests
02:56:00 - Pagerduty tries to notify me of outage via email, phone and mobile app
09:01:00 - I wake up and see the notifications
09:02:02 - Backend is restarted and recovers

Root cause analysis

All ~24k HTTP requests that reached the backend during the outage failed with the following exception:

Write access control for binary caches

support@cachix.org (Domen Kožar) — Tue, 10 Nov 2020 11:00:00 +0000

As Cachix is growing, I have noticed a few issues along the way: Signing keys are still the best way to upload content and not delegate trust to Cachix, but users have also found that they can be difficult to manage, particularly if the secret key needs to be rotated.

At this point, the best option is to clear out the cache completely, and re-sign everything with a newly generated key. Since the clients require the public key, rolling out a new key-pair can be somewhat complicated.

Changes to Garbage Collection

support@cachix.org (Domen Kožar) — Thu, 01 Oct 2020 09:00:00 +0000

Based on your feedback, I have made the following two changes:

When downloading <store-hash>.narinfo the timestamp of last access is updated, previously this would happen only with nar archives.

This change allows tools like nix-build-uncached to prevent unneeded downloads and playing nicely with Cachix garbage collection algorithm!
Previously, the algorithm ordered paths first by last accessed timestamp and then by creation timestamp.

That worked well until you had all entries with last accessed and all newly created store paths will get deleted first.

Upstream caches: avoiding pushing paths in cache.nixos.org

support@cachix.org (Domen Kožar) — Tue, 28 Jul 2020 14:30:00 +0000

One of the most requested features, the so-called upstream caches was released today.

It is enabled by default for all caches, and the owner of the binary cache can disable it via Settings.

When you push store paths to Cachix, querying cache.nixos.org adds overhead of multiples of 100ms, but you save storage and possibly minutes for avoiding the pushing of already available paths.

Queries to cache.nixos.org are also cached, so that subsequent push operations do not have the overhead.

Documentation and More Documentation

support@cachix.org (Domen Kožar) — Mon, 20 Jul 2020 14:45:00 +0000

Documentation is an important ingredient of a successful software project.

Last few weeks I’ve worked on improving status quo on two fronts:

https://nix.dev is an opinionated guide for developers getting things done using the Nix ecosystem.

A few highlights:
- Getting started repository template with a tutorial for using declarative and reproducible developer environments
- Setting up GitHub Actions with Nix
- Nix language anti-patterns to avoid and recommended alternatives
- Building docker images with Nix

Proposal for improving Nix error messages

support@cachix.org (Domen Kožar) — Wed, 18 Mar 2020 08:00:00 +0000

I’m lucky to be in touch with a lot of people that use Nix day to day.

One of the most occouring annoyances that pops up more frequently with those starting with Nix are confusing error messages.

Since Nix community has previously succesfully stepped up and funded removal of Perl to reduce barriers for source code contributions, I think we ought to do the same for removing barriers when using Nix.

CDN and double storage size

support@cachix.org (Domen Kožar) — Wed, 29 Jan 2020 08:00:00 +0000

Cachix - Nix binary cache hosting, has grown quite a bit in recent months in terms of day to day usage and that was mostly noticable on bandwidth.

Over 3000 GB were served in December 2019.

CDN by CloudFlare

Increased usage prompted a few backend machine instance upgrades to handle concurrent upload/downloads, but it became clear it’s time to abandon single machine infrastructure.

As of today, all binary caches are served by CloudFlare CDN.