arangosh> db.ids.ensureIndex({ type: "skiplist", fields: [ "myId" ], unique: true }); { "deduplicate" : true, "fields" : [ "myId" ], "id" : "ids/18089", "isNewlyCreated" : true, "sparse" : false, "type" : "skiplist", "unique" : true, "code" : 201 } arangosh> db.ids.save({ "myId": 123 }); { "_id" : "ids/18092", "_key" : "18092", "_rev" : "_V8R1UJm--_" } arangosh> db.ids.save({ "myId": 456 }); { "_id" : "ids/18096", "_key" : "18096", "_rev" : "_V8R1UJm--B" } arangosh> db.ids.save({ "myId": 789 }); { "_id" : "ids/18099", "_key" : "18099", "_rev" : "_V8R1UJm--D" } arangosh> db.ids.save({ "myId": 123 }); [ArangoError 1210: unique constraint violated - in index 18089 of type skiplist over ["myId"]; conflicting key: 18092]