Postgres supports Unix sockets when running on the same machine. That’s what I use, for a significant latency improvement over the TCP stack even at 127.0.0.1.

"...has orders of magnitude less latency than..."

[citation needed]. Local network access shouldn't be much different than local IPC.

Perhaps I wasn't clear enough in my comment. When I said "database latency is generally miniscule compared to internet round-trip latency", I meant between the user and the website. Because they're often thousands of miles away, there are network buffers, etc.

But no, a local network hop doesn't introduce "orders of magnitude" more latency. The article itself describes how it is only 5x slower within a datacenter for the roundtrip part -- not 100x or 1,000x as you are claiming. But even that is generally significantly less than the time it takes the database to actually execute the query -- so maybe you see a 1% or 5% speedup of your query. It's just not a major factor, since queries are generally so fast anyways.

The kind of database latency that you seem to be trying to optimize for is a classic example of premature optimization. In the context of a web application, you're shaving microseconds for a page load time that is probably measured in hundreds of milliseconds for the user.

> I don't get to decide this. The business does.

You have enough power to design the entire database architecture, but you can't write and execute queries more efficiently, following best practices?

If you're concerned about the overhead of IPC when using postgres on the same server, weigh your intuition of it against your intuition of the savings from having a persistent process. SQLite can't cache a lot of things because some other process might have completely changed the database between transactions. Postgres knows everything that happens to the database.