Prisma is one of the runtime currently supported [1]. Metatype enables you to compose multiple runtimes together. Let's say you have model/struct product (id, name, similarProducts), the two first attributes may be stored in Prisma (like you would do it normally), the third one can come from another runtime such as an HTTP api and the engine will take care of resolving the data together. You can also add an authorization policy on any of the fields.

[^1] https://metatype.dev/docs/reference/runtimes