arangosh> db.ids.ensureIndex({ type: "skiplist", fields: [ "myId" ], unique: true }); { "id" : "ids/15933", "type" : "skiplist", "fields" : [ "myId" ], "unique" : true, "sparse" : false, "isNewlyCreated" : true, "code" : 201 } arangosh> db.ids.save({ "myId": 123 }); { "_id" : "ids/15936", "_key" : "15936", "_rev" : "15936" } arangosh> db.ids.save({ "myId": 456 }); { "_id" : "ids/15940", "_key" : "15940", "_rev" : "15940" } arangosh> db.ids.save({ "myId": 789 }); { "_id" : "ids/15943", "_key" : "15943", "_rev" : "15943" } arangosh> db.ids.save({ "myId": 123 }); [ArangoError 1210: cannot create document, unique constraint violated]