arangosh> db.ids.ensureIndex({ type: "skiplist", fields: [ "myId" ], unique: true }); { "id" : "ids/15412", "type" : "skiplist", "fields" : [ "myId" ], "unique" : true, "sparse" : false, "isNewlyCreated" : true, "code" : 201 } arangosh> db.ids.save({ "myId": 123 }); { "_id" : "ids/15415", "_key" : "15415", "_rev" : "_V_qEiiS---" } arangosh> db.ids.save({ "myId": 456 }); { "_id" : "ids/15419", "_key" : "15419", "_rev" : "_V_qEiiW---" } arangosh> db.ids.save({ "myId": 789 }); { "_id" : "ids/15422", "_key" : "15422", "_rev" : "_V_qEiia---" } arangosh> db.ids.save({ "myId": 123 }); [ArangoError 1210: cannot create document, unique constraint violated]