At my last job I wrote equivalent Python and Haskell web services for a talk.
My goal was to show off how much simpler the code is for Haskell web services than Python, but my coworkers only wanted to know if it was faster.
I did the apache benchmark tests, and up to the 99 percentile, requests to the Haskell webservice took less than one tenth of the time hitting the Python webservice. That last fraction of a percent took longer, in rare cases, much much longer.
I now get paid to write Haskell webservices, but this is a thing to keep in mind! Sometimes the laziness and garbage collection fires just the wrong way.
I haven’t tried the same thing since the low latency garbage collector has been merged, maybe this isn’t as much of a problem now?