arangosh> db.ids.ensureIndex({ type: "skiplist", fields: [ "myId" ], unique: true }); { "id" : "ids/16102", "type" : "skiplist", "fields" : [ "myId" ], "unique" : true, "sparse" : false, "isNewlyCreated" : true, "code" : 201 } arangosh> db.ids.save({ "myId": 123 }); { "_id" : "ids/16105", "_key" : "16105", "_rev" : "16105" } arangosh> db.ids.save({ "myId": 456 }); { "_id" : "ids/16109", "_key" : "16109", "_rev" : "16109" } arangosh> db.ids.save({ "myId": 789 }); { "_id" : "ids/16112", "_key" : "16112", "_rev" : "16112" } arangosh> db.ids.save({ "myId": 123 }); [ArangoError 1210: cannot create document, unique constraint violated]