arangosh> a1 = db.example.insert({ a : 1 }); { "_id" : "example/16155", "_key" : "16155", "_rev" : "_XiAwU0---_" } arangosh> a2 = db._replace(a1, { a : 2 }); { "_id" : "example/16155", "_key" : "16155", "_rev" : "_XiAwU0---B", "_oldRev" : "_XiAwU0---_" } arangosh> a3 = db._replace(a1, { a : 3 }); [ArangoError 1200: precondition failed]