arangosh> db.ids.ensureIndex({ type: "skiplist", fields: [ "myId" ], unique: true }); { "deduplicate" : true, "fields" : [ "myId" ], "id" : "ids/18652", "isNewlyCreated" : true, "sparse" : false, "type" : "skiplist", "unique" : true, "code" : 201 } arangosh> db.ids.save({ "myId": 123 }); { "_id" : "ids/18655", "_key" : "18655", "_rev" : "_XGh_a-6--_" } arangosh> db.ids.save({ "myId": 456 }); { "_id" : "ids/18659", "_key" : "18659", "_rev" : "_XGh_a-6--B" } arangosh> db.ids.save({ "myId": 789 }); { "_id" : "ids/18662", "_key" : "18662", "_rev" : "_XGh_a-6--D" } arangosh> db.ids.save({ "myId": 123 }); [ArangoError 1210: unique constraint violated - in index 18652 of type skiplist over ["myId"]; conflicting key: 18655]