diff --git a/.env b/.env
index 1226cb23..00f188dc 100644
--- a/.env
+++ b/.env
@@ -5,10 +5,6 @@ DOMAIN=localhost
 # To test the local Traefik config
 # DOMAIN=localhost.tiangolo.com
 
-# Public frontend URL, used by the backend to generate links in emails.
-# Deployments derive this from DOMAIN in compose.deploy.yml.
-FRONTEND_HOST=http://localhost:5173
-
 # Environment: local, staging, production
 ENVIRONMENT=local
 
@@ -31,7 +27,6 @@ SMTP_PORT=1025
 
 # Postgres
 POSTGRES_SERVER=localhost
-POSTGRES_PORT=5432
 POSTGRES_DB=app
 POSTGRES_USER=postgres
 POSTGRES_PASSWORD=changethis
diff --git a/compose.override.yml b/compose.override.yml
index d09cf64f..5fc0ec37 100644
--- a/compose.override.yml
+++ b/compose.override.yml
@@ -88,15 +88,15 @@ services:
     depends_on:
       - backend
       - mailcatcher
-    env_file:
-      - .env
     environment:
+      - FIRST_SUPERUSER=${FIRST_SUPERUSER?Variable not set}
+      - FIRST_SUPERUSER_PASSWORD=${FIRST_SUPERUSER_PASSWORD?Variable not set}
       - PLAYWRIGHT_BASE_URL=http://backend:8000
       - VITE_API_URL=http://backend:8000
       - MAILCATCHER_HOST=http://mailcatcher:1080
       # For the reports when run locally
       - PLAYWRIGHT_HTML_HOST=0.0.0.0
-      - CI=${CI}
+      - CI=${CI:-}
     volumes:
       - ./frontend/blob-report:/app/frontend/blob-report
       - ./frontend/test-results:/app/frontend/test-results
diff --git a/compose.yml b/compose.yml
index 3c5e73cd..e9b34254 100644
--- a/compose.yml
+++ b/compose.yml
@@ -27,8 +27,6 @@ services:
       timeout: 10s
     volumes:
       - app-db-data:/var/lib/postgresql
-    env_file:
-      - .env
     environment:
       - POSTGRES_PASSWORD=${POSTGRES_PASSWORD?Variable not set}
       - POSTGRES_USER=${POSTGRES_USER?Variable not set}
@@ -59,7 +57,6 @@ services:
         condition: service_completed_successfully
     # The YAML anchor lets the prestart service reuse this environment mapping.
     environment: &backend-environment
-      FRONTEND_HOST: ${FRONTEND_HOST?Variable not set}
       ENVIRONMENT: ${ENVIRONMENT}
       PROJECT_NAME: ${PROJECT_NAME?Variable not set}
       BACKEND_CORS_ORIGINS: ${BACKEND_CORS_ORIGINS}
@@ -71,7 +68,6 @@ services:
       SMTP_PASSWORD: ${SMTP_PASSWORD}
       EMAILS_FROM_EMAIL: ${EMAILS_FROM_EMAIL}
       POSTGRES_SERVER: db
-      POSTGRES_PORT: ${POSTGRES_PORT}
       POSTGRES_DB: ${POSTGRES_DB}
       POSTGRES_USER: ${POSTGRES_USER?Variable not set}
       POSTGRES_PASSWORD: ${POSTGRES_PASSWORD?Variable not set}
diff --git a/deployment.md b/deployment.md
index 1485c6ba..5f3dbb76 100644
--- a/deployment.md
+++ b/deployment.md
@@ -89,8 +89,6 @@ You can set several other environment variables:
 * `SMTP_USER`: The SMTP server user to send emails.
 * `SMTP_PASSWORD`: The SMTP server password to send emails.
 * `EMAILS_FROM_EMAIL`: The email account to send emails from.
-* `POSTGRES_SERVER`: The hostname of the PostgreSQL server. You can leave the default of `db`, provided by the same Docker Compose. You normally wouldn't need to change this unless you are using a third-party provider.
-* `POSTGRES_PORT`: The port of the PostgreSQL server. You can leave the default. You normally wouldn't need to change this unless you are using a third-party provider.
 * `POSTGRES_USER`: The Postgres user, you can leave the default.
 * `POSTGRES_DB`: The database name to use for this application. You can leave the default of `app`.
 * `SENTRY_DSN`: The DSN for Sentry, if you are using it.