More than once I run into db serialization performance issues. Postgres reports all nice and fast, yet requests are slow. It took me a while to figure out that activerecord was busy converting my data into one large query string, and then busy sending that string over the wire. The issue was a field using postgres jsonb and I was filling in a large array of text lines in some cases. Workarounds are easy but I never pinned down why it would take multiple 100‘s of milliseconds to serialize into sql.