Question:
When I go to create an RDS database, the db.t2.micro database is not showing up for PostgreSQL. 
I have the “Include previous generation classes” box checked. The instance type is showing for MySQL but not PostgreSQL.
Answer:
I think when aws adds a new version of database, it offers only the old version as a free tier. Currently postgres 13 is available but only lower than 13 has free tier
