You can have nix-ci automatically pull from, and push to, Cachix.

Step 1: Configuration

To activate cachix integration, configure the name and public-key in your flake's nix-ci.cachix configuration.

nix-ci = {
  cachix = {
    name = "foo-bar";
    public-key = "";

Step 2: Secret

You will also need to create a cachix auth token and configure it as a secret for your repository on nix-ci with the name: CACHIX_AUTH_TOKEN

Reference schema

# Cachix
cachix: # optional
  # Cachix configuration
  # In order to push to the cache as well, the repository needs to have a CACHIX_AUTH_TOKEN or CACHIX_SIGNING_KEY secret.
  # CachixConfiguration
  name: # required
    # cache name
  public-key: # required
    # cache public key (for pulling)