You can do both, write internal or external APIs with GraphQL or REST. On GraphQL maybe is better because already has Schema documentation that saves a lot of time on documenting the API. RPC fits best to a machine-to-machine case, but there are some downsides like the time to develop an API using it, time to document it.

Store and query relational data on the cloud. Make it accessible over GraphQL and REST with a scalable, open-source backend, based on the Parse Platform.

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