arangosh> a1 = db.example.insert({ a : 1 }); { "_id" : "example/17801", "_key" : "17801", "_rev" : "_W-M-Y9W--_" } arangosh> a2 = db._replace(a1, { a : 2 }); { "_id" : "example/17801", "_key" : "17801", "_rev" : "_W-M-Y9W--B", "_oldRev" : "_W-M-Y9W--_" } arangosh> a3 = db._replace(a1, { a : 3 }); [ArangoError 1200: precondition failed]