gRPC InvalidArgument or FailedPrecondition if system cannot be updated

Suppose we have a gRPC DB-backed application with some resource X like this, for example in Go:

type X struct {
    id      string
    name    string
    version string
}

And for some reason the application does not permit updates unless version = "2".

If a client tries to make a request to update the name of an existing resource whose version = "1", like this:

// This exists in the DB.
x := X{
    id:      "xyz",
    version: "1",
    name:    "some name",
}

UpdateX(
    X{
        id:      "xyz",
        name:    "some other name",
    },
) 

what gRPC error code should be returned?

Referring to the codes here: https://grpc.github.io/grpc/core/md_doc_statuscodes.html, I can see arguments for both INVALID_ARGUMENT and FAILED_PRECONDITION.

INVALID_ARGUMENT:

• The resource cannot be updated so the request will always fail, and is hence invalid

FAILED_PRECONDITION:

• The state of the system needs to be checked to see what the version of the resource is, you can't determine a priori whether the request is possible
• Even though the system currently does not allow such updates, in theory it could be updated so that the request becomes acceptable

Based on your description, you should probably use FAILED_PRECONDITION. Like mentioned in https://grpc.github.io/grpc/core/md_doc_statuscodes.html: INVALID_ARGUMENT indicates arguments that are problematic. But in your case the arguments is correct, but the system does not allow update, thus I think FAILED_PRECONDITION is a better fit.