Keep heavy imports off the django.setup() path that every process (web, celery, temporal, migrate, shell, CI) pays for. Use when touching AppConfig.ready(), wiring signal receivers, editing the lazy API router (posthog/api/rest_router.py or its __init__.py shim), deferring a heavy import, when the startup-import-budget guard fails, or when merging master into a long-lived branch that made the router lazy.