[mplanchard]

An unexpected benefit of nix for me was CI caching. It’s easy to set up S3 as a binary cache, and then anything you can express as a nix derivation can be cached so that if nothing has changed, it avoids a build.

One fun example is the test database: five years of accumulated migrations were relatively slow to run in various portions of the pipeline. I made a nix derivation that runs postgres, runs migrations, seeds some test data, runs some tests, and then saves the data directory into $out. CI jobs can then load the DB by building that derivation and copying the data files into a local directory. If no migrations or other dependencies have changed, this is virtually instantaneous.

[bigyabai]

My last gig was at a place where a guy basically wrote his own job security by reducing a 1hr 40min JS build pipeline down to 2 minutes with Nix caching.

[remram]

FYI by calling it "job security" you imply that this nix caching approach is unmaintainable.

[bigyabai]

It's implied because it's true. Throw away the content-adressable cache index and you're back to 2 hour development velocity, so the Nix guy probably gave himself a decade and a half of runway for a workload that mostly amounts to periodically running `nix flake update` and shuffling around version hashes.

We already saw this same trend happen where "the CMake guy" or "the Xcode guy" gets wheeled in to solve their domain-specific issue in large enough orgs. I was impressed by this guy's initiative to carve out an equally indispensable niche.

[pxc]

In truth, the "job security" thing is often as much a matter of personality as it is explicit strategy. The "XYZ guy" often becomes that person simply by being someone who is stubborn enough to tackle integration problems most people would rather avoid, and by being willing to deeply embrace "RTFM".

To say they've established "job security" can sometimes seem like a cynical read on their roles, but I think it's always good for teams to have a few devs with this sort of personality.

[pxc]

He made himself useful by practicing an uncommon skill, so I understand why it was put that way.

But Nix is plenty learnable and Nix hires are possible, so I see what you mean.

[cjbgkagh]

Interesting, I have my own hacked together caches to greatly speed up docker setup, having a cache at this level may speed things up further in a cleaner more maintainable way.