Supercharging Nix deployments with FlakeHub Cache

Today, I’m excited to share how FlakeHub Cache can dramatically improve your Nix development and deployment workflow. While our Magic Nix Cache has helped teams boost CI performance over the past year, FlakeHub Cache represents the next evolution - accelerating builds and fundamentally transforming how Nix deployments work. We’ll examine a Home Manager configuration that demonstrates how FlakeHub Cache’s pre-built closures and pre-evaluated store paths can make deployments both faster and more reliable, especially in resource-constrained environments. If you’re currently using Magic Nix Cache, which will reach end-of-life for its free tier on February 1st, 2025, this is the perfect time to explore how FlakeHub Cache can enhance your entire Nix workflow.

The challenge with traditional Nix deployments

If you’ve worked with Nix, you’re likely familiar with the standard deployment flow: evaluate Nix expressions, realise closures, and download or build missing dependencies. While this works, it can be time-consuming and resource-intensive, especially when deploying to multiple machines or CI environments.

Enter FlakeHub Cache

FlakeHub Cache fundamentally changes how Nix deployments work by eliminating build time and evaluation overhead. Here’s why this matters:

Traditional Nix deployments, even with a binary cache, require two steps that can be resource-intensive:

• Evaluation: Nix must evaluate your configuration to determine the store paths it needs - this alone can overwhelm memory-constrained devices
• Realization: Nix then either builds those paths or downloads them from a binary cache

FlakeHub Cache eliminates both steps. When you push configurations through CI, FlakeHub:

• Evaluates and stores the exact store paths your configuration needs
• Caches the built closures for those paths

Using FlakeHub Cache when deploying means you can bypass Nix evaluation entirely:

fh apply home-manager "determinatesystems/home-manager-example/*#homeConfigurations.linuxUsername@linuxHostname"

This single command is transformative - especially for resource-constrained environments where evaluating a Nix configuration could cause out-of-memory errors. FlakeHub already knows the store paths needed, so no local Nix evaluation is required. It fetches the pre-built closure and activates it.

Real benefits for real teams

What makes this approach particularly powerful?

• Zero evaluation overhead: Skip not just building but even the memory-intensive process of evaluating Nix expressions
• Resource efficient: Deploy to severely constrained environments that couldn’t even evaluate complex Nix configurations
• Consistent environments: Every machine gets bit-for-bit identical outputs
• CI verified: Configurations are pre-tested before reaching production
• Bandwidth optimized: Only download what you need

See it in action

We’ve created a complete example repository that demonstrates these concepts. The configuration supports both macOS and Ubuntu systems, showing how to:

• Structure your flake for multi-platform support
• Configure GitHub Actions to build and cache your configurations
• Deploy configurations rapidly using fh

Check out the complete example on GitHub to see how it all fits together.

Beyond Home Manager

While this example focuses on Home Manager, the same principles apply to:

• NixOS system configurations
• nix-darwin configurations
• Development environments
• Custom tooling and packages

The benefits become even more pronounced with larger configurations that traditionally require significant build time.

Getting started

Ready to supercharge your own Nix deployments? Here’s how to get started:

1. Sign up for FlakeHub to get access to FlakeHub Cache.
2. Get one month free by applying the coupon code FHC during checkout. If you’re a maintainer of an open source project, contact us at support@flakehub.com for a free account.
3. Review our comprehensive documentation to learn more about FlakeHub’s capabilities.
4. Follow our getting started guide to begin your journey.

Join the revolution

FlakeHub Cache represents a fundamental shift in how we think about Nix deployments. By moving computation from deployment time to build time, we’re making Nix more accessible and practical for teams of all sizes.

Have questions or want to learn more? Join us on Discord. We’d love to hear about your use cases and help you get started with FlakeHub Cache.

Remember: your deployments should be boring and predictable, providing a sense of security and stability. With FlakeHub Cache, they can be.