A practical performance budget for launch

The smallest useful fragment endpoint proves the whole pipeline: a button, an HTMX attribute, and a Django view that returns the server time as an HTML fragment.

The endpoint

/fragment/ping/ renders the current timestamp into a small div. A request with the HX-Request header swaps it into the page — no JSON, no re-render of the document, no client state.

from django.http import HttpResponse
from django.utils import timezone

def server_time(request):
    now = timezone.now().isoformat()
    if request.headers.get('HX-Request'):
        return HttpResponse(f'
{now}
')
    return HttpResponse(f'
Server time: {now}
')

Why it matters

If a five-line fragment endpoint works end to end, the heavier regions — contact forms, newsletter signup, product filters — ride the same rails. The demo is trivial; the architecture it proves is not.