What purpose does the default service serve in Google's app engine

Question

When deploying an app with a microservices architecture to google's app engine, it requires one of my services to be the default service.

Why is this required and does the default service behave any differently to any other 'named' service?

Answer 1

Here would be some roles/reasons for the default service (I'm fairly sure the list is not exhaustive):

• the fallback destination for routing a request using a dispatch.yaml file if none of the routing rules is matched
• the fallback destination for cron jobs if they aren't specifically configured to target a specific service
• for initial deployment of app-level configs, see Why do I need to deploy a "default" app before I can deploy multiple services in GCP?

Practically I'd consider such differences just extra functionality (mostly infra-related) compared to the named services, otherwise they're very similar.