arangosh> db.ids.ensureIndex({ type: "skiplist", fields: [ "myId" ], unique: true }); { "deduplicate" : true, "fields" : [ "myId" ], "id" : "ids/111813", "isNewlyCreated" : true, "sparse" : false, "type" : "skiplist", "unique" : true, "code" : 201 } arangosh> db.ids.save({ "myId": 123 }); { "_id" : "ids/111816", "_key" : "111816", "_rev" : "_YYClXii--_" } arangosh> db.ids.save({ "myId": 456 }); { "_id" : "ids/111820", "_key" : "111820", "_rev" : "_YYClXim--_" } arangosh> db.ids.save({ "myId": 789 }); { "_id" : "ids/111823", "_key" : "111823", "_rev" : "_YYClXim--B" } arangosh> db.ids.save({ "myId": 123 }); [ArangoError 1210: unique constraint violated - in index 111813 of type skiplist over ["myId"]; conflicting key: 111816]