Easy to Overlook PostgreSQL Performance Issues in Rails Apps

If your database uses an SSD disk (hint: it does), these default settings will likely harm your app’s performance. As a result your database is less likely to choose an index instead of a sequential scan. Seq scans are both CPU and memory-intensive. To find matching rows, the database engine has to well scan each row individually. It’s like doing a for loop over a large array instead of fetching a value based on its hash key.