> The need for PostgreSQL to modify all of a table’s indexes for each update has several performance implications. Obviously, this makes update queries slower because the system has to do more work.
You know, I was wondering something regarding this write amplification. It's true that MySQL doesn't need to update its indexes like that. However, MySQL replication relies on the binlog, where every change has to be written in addition to the database itself (InnoDB redo log and so on). So, it seems to me, MySQL, if used in a cluster, has a different kind of write amplification. One that PostgreSQL does not have, because it reuses its WAL for the replication.
In addition, on the receiving side, MySQL first writes the incoming binlog to the relay log. The relay log is then consumed by the applier threads, creating more InnoDB writes and (by default) more binlog.