At that point you’ve implemented a constant-time algorithm.

It works quite well in practice though. I wonder if you could make an ergonomic library for it.

Just add a macro to a function and it'll keep track of how long past executions took to execute and add artificial delays to ensure all subsequent executions are at least that long. If they're longer, extend the minimum time by 2x.

Perhaps apply an AIMD algorithm to it? Though there's still room for exploitation there, it'd just take a lot longer to find. Just letting the programmer specify the minimum time might be better in practice.

It can be implemented once, by, say, nginx and enabled by a devops instead of every random outsourced java webapp.