While checking my API metrics in new relic and found queries are getting executed with response time in a few ms, but there is a field for #PID<0.30881.849> which took 300ms+ to process.
Reason why you are not getting almost any answers is that what you are asking is basically someone else to do your work for you. Also they can’t give you any answers because they don’t have access to your code and if they did they would have to what you need to do and that is to find out what part of your code is slow. If someone asked something like that from you would you be able to answer?
I don’t work with Elixir professionally but first thing I would do is to find out what parameters where given to the request. Then try to get same problem appear in your local environment and start profiling. I haven’t yet used any Elixir/BEAM profiling tools because I haven’t had any performance problems with my small projects. With small bit of googling I found this blog how to do performance profiling in Elixir https://medium.com/@victor.nascimento/an-elixir-performance-tooling-story-c5c85479063a