PostgreSQL table option where the write-ahead log isn't written — much faster than normal storage but wiped if the database crashes or restarts. Functionally a cache. Supported in Rails migrations since ~Rails 6. In RSpec, appending a one-liner that forces unlogged creation for all test tables shaved ~3.5 minutes off a bad test suite and ~20s off a good one with no code changes. Great for CI (fresh DB every run) but confusing on local dev — Docker restarts silently empty the tables, forcing a migration re-run.