It can really slow things down if your views start calling other views in since they’re not actually tables
They can be in some cases! There’s a type of view called an “indexed” or “materialized” view where the view data is stored on disk like a regular table. It’s automatically recomputed whenever the source tables change. Doesn’t work well for tables that are very frequently updated, though.
Having said that, if you’re doing a lot of data aggregation (especially if it’s a sproc that runs daily), you’d probably want to set up a separate OLAP database so that large analytical queries don’t slow down transactional queries. With open-source technologies, this is usually using Hive and Presto or Spark combined with Apache Airflow.
Also, if you have data that’s usually aggregated by column, then a column-based database like Clickhouse is usually way faster than a regular row-based database. These store data per-column rather than per-row, so aggregating one column across millions or even billions of rows (eg average page load time for all hits ever recorded) is fast.