Environment mixins ¶

An environment mixin is a partial manifest that Nais merges over a base manifest for a specific environment. It lets one set of manifests serve several environments, so you can run different configuration in dev and prod without duplicating the whole manifest.

You keep a base file (.nais/app.yaml) with the shared and development configuration, and one file per environment named .nais/app.<environment>.yaml with that environment's overrides. When you run nais apply with --environment <environment>, the CLI deep-merges the matching mixin over the base before deploying.

Mixins replace the old Handlebars templating approach. Instead of a template plus a variables file rendered by nais/deploy, you write plain manifests that merge together. The result is valid YAML at every step, so editors and validators understand it, and there is no separate templating engine to reason about.

Merge rules ¶

The merge follows two rules:

Maps and scalars are overridden. A field set in the mixin replaces the same field in the base.
Lists are concatenated. Items in the mixin are appended to the base list, not replaced.

Map override example ¶

A base manifest with default replicas and resource requests:

.nais/app.yaml

spec:
  replicas:
    min: 1
    max: 1
  resources:
    requests:
      cpu: 20m
      memory: 64Mi

A production mixin that raises them:

.nais/app.prod.yaml

spec:
  replicas:
    min: 2
    max: 4
  resources:
    requests:
      cpu: 100m
      memory: 256Mi

Applying with --environment prod produces:

merged result

spec:
  replicas:
    min: 2
    max: 4
  resources:
    requests:
      cpu: 100m
      memory: 256Mi

The mixin's replicas and resources maps replace the base values entirely.

List concatenation gotcha ¶

Lists behave differently. If your base sets an environment variable and your mixin tries to override it, you get both entries:

.nais/app.yaml

spec:
  env:
    - name: LOG_LEVEL
      value: debug

.nais/app.prod.yaml

spec:
  env:
    - name: LOG_LEVEL
      value: info

merged result — not what you want

spec:
  env:
    - name: LOG_LEVEL
      value: debug
    - name: LOG_LEVEL
      value: info

Both entries end up in the manifest. Keep per-environment values in map fields and avoid using mixins to change list fields like spec.env.

For a complete pipeline that uses mixins across multiple environments, see Set up a complete deploy pipeline.