Preview environments for Polyglot.

Most real applications are polyglot by the time they hit three engineers. A Next.js frontend, a Go API, a Python worker, Postgres, a cache, an object store. Galley treats this as the default shape, not an edge case.

The config

version: 1

services:
  web:
    kind: web
    build:
      path: ./web              # Next.js
    expose: 3000
    depends_on: [api]
    env:
      NEXT_PUBLIC_API_URL: "https://${GALLEY_PREVIEW_HOST_api}"

  api:
    kind: api
    build:
      path: ./api              # Go
    expose: 8080
    depends_on: [postgres, cache, objstore]
    env:
      DATABASE_URL: postgres://app:pw@postgres:5432/app
      REDIS_URL: redis://cache:6379/0
      S3_ENDPOINT: http://objstore:9000
      S3_BUCKET: myapp-uploads
      S3_ACCESS_KEY: minio
      S3_SECRET_KEY: minio12345

  worker:
    kind: worker
    build:
      path: ./worker           # Python
      start: "python -m worker"
    depends_on: [postgres, cache]
    env:
      DATABASE_URL: postgres://app:pw@postgres:5432/app
      REDIS_URL: redis://cache:6379/0

  postgres:
    kind: database
    image: postgres:16-alpine
    expose: 5432
    env:
      POSTGRES_USER: app
      POSTGRES_PASSWORD: pw
      POSTGRES_DB: app

  cache:
    kind: cache
    image: redis:7-alpine
    expose: 6379

  objstore:
    kind: other
    image: minio/minio:latest
    expose: 9000
    env:
      MINIO_ROOT_USER: minio
      MINIO_ROOT_PASSWORD: minio12345

Multi-web-service note: when there’s both a web and an api (or two web services), each lands at a named subdomain — web.pr-N-..., api.pr-N-.... Use ${GALLEY_PREVIEW_HOST_<service>} in env values to thread the right URL into the right place (here, the frontend’s NEXT_PUBLIC_API_URL resolves to the backend’s preview host at deploy time).

The usual gotcha

Detection is conservative for polyglot repos. With web/, api/, and worker/ directories, Galley relies on your explicit build.path per service rather than guessing — write the services: block fully, don’t expect autodetect to work it out across subdirectories.

If you hit something unexpected, the galley.yml reference covers every field with constraints. Email if anything’s missing or surprising.