arangosh> db.ids.ensureIndex({ type: "skiplist", fields: [ "myId" ], unique: true }); { "id" : "ids/15233", "type" : "skiplist", "fields" : [ "myId" ], "unique" : true, "sparse" : false, "isNewlyCreated" : true, "code" : 201 } arangosh> db.ids.save({ "myId": 123 }); { "_id" : "ids/15236", "_key" : "15236", "_rev" : "_U-_q2z2---" } arangosh> db.ids.save({ "myId": 456 }); { "_id" : "ids/15240", "_key" : "15240", "_rev" : "_U-_q2z6---" } arangosh> db.ids.save({ "myId": 789 }); { "_id" : "ids/15243", "_key" : "15243", "_rev" : "_U-_q2z6--_" } arangosh> db.ids.save({ "myId": 123 }); [ArangoError 1210: cannot create document, unique constraint violated]