Document with the requested ID already exists.

I'm getting an error when trying to create a 2nd document in a collection....

I've made a VueJs ui that allows a user to update a collection of documents, after the first document was created all documents that in that collection throws the error in the title. I am not assigning an id on create and using the unique() approach. Here is the js for my home rolled upsert function:

saveLayer : ( data, layerId ) => {
if( layerId == undefined ){
return api.provider().database.createDocument( Server.database, Server.collections.layers, "unique()", data );
} else {
return api.provider().database.updateDocument( Server.database, Server.collections.layers, layerId, data );
}
}

for the first createDocument everything works as expected, with the document created as expected and then the second document (and 3rd and 4th or how many documents need creating) fails with that error. The payload on the web request sent out looks good as in the attach screen capture. I've deleted the document causing the duplicate from the collection and get the same issue again (but the document id is different).

Any pointers as what I'm doing wrong ?

Thanks

Do you have a unique index on the collection?

yes, I misunderstood the error message, I thought it was related to the id I was created as opposed to the id I was creating. My bad. Thanks for the help.

No worries. It is a little misleading