The idea is that your server handler mimics those steps and contains all the IO you need (aka external depdendencies). The receiving and sending of the http req

The idea is that your server handler mimics those steps and contains all the IO you need (aka external depdendencies). The receiving and sending of the http requests + any other I/O you need should be immediately visible in the top level method (in a simple model). Everything below is functional and pure. Take a request, use pure functions to transform and reshape the data, pass that back up the call-stack to the top level method. Do some I/O operation against the database, go into functional land to shape it a bit, bring it back up, combine with other data in a pure way and then finally send the response.