On your own, please set up and configure PostGresSQL. You can use one of these tutorials:
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https://www.tutorialspoint.com/postgresql/postgresql_environment.htm
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https://www.codementor.io/engineerapart/getting-started-with-postgresql-on-mac-osx-are8jcopb
PostgresSQL is an open source database, which you can use to write and read data in your app. Why use Postgres? There is some information here: https://www.compose.com/articles/what-postgresql-has-over-other-open-source-sql-databases/