arangosh> db.ids.ensureIndex({ type: "skiplist", fields: [ "myId" ], unique: true }); { "id" : "ids/1139258929", "type" : "skiplist", "fields" : [ "myId" ], "unique" : true, "sparse" : false, "isNewlyCreated" : true, "code" : 201 } arangosh> db.ids.save({ "myId": 123 }); { "_id" : "ids/1139521073", "_rev" : "1139521073", "_key" : "1139521073" } arangosh> db.ids.save({ "myId": 456 }); { "_id" : "ids/1139717681", "_rev" : "1139717681", "_key" : "1139717681" } arangosh> db.ids.save({ "myId": 789 }); { "_id" : "ids/1139914289", "_rev" : "1139914289", "_key" : "1139914289" } arangosh> db.ids.save({ "myId": 123 }); [ArangoError 1210: cannot create document, unique constraint violated]