how to add a query to postgres and have it show up as a table

I'm not sure what technology I need because I'm not a DBA, but I'm sure there's a good way to do this. I have a postgres database with this schema (top two tables exist): **So I'm trying to add the 3rd table to the database. It's a subset of observation: all latest observations by stream_id and target_id with the target_key value already joined into it.** I know upfront that 99% of the queries against the target table are asking for the latest row of a certain stream_id and target_id. so I thought instead of manually building another table with duplicate data, I'll try to leverage the power of the database to make a temporal table, or a foreign data wrapper or something, that is essentially a hard coded query on the database which looks like a table we can query, (and since it's querying a subset of the data, its much faster). Ok, so that's what I'm looking for but I don't know which technology to use, as I mentioned I've been searching and I found temporal tables, virtual tables and FDW. But I'm a programmer not a DBA so I'm having a hard time telling the difference or understanding which one matches my need. What technology can I use for this?