Without a CDN, every user crosses the planet

1def request(url):
2    # DNS resolves to the one origin in us-east
3    origin_ip = dns.resolve(origin_host)
4 
5    # one TCP+TLS handshake, then the GET — each
6    # leg of the trip costs (distance / c) milliseconds
7    conn = tcp.connect(origin_ip)        # 1 RTT
8    conn.send(http.get(url))             # 1 RTT
9    response = conn.recv()               # waits here
10 
11    return response  # total wait ~= rtt_to(us-east)

1rps_counter = 0  # what the gauge above the box reads
2 
3def serve_forever():
4    while True:
5        conn = listener.accept()  # next user, anywhere
6        rps_counter += 1          # +1 per arriving request
7 
8        req = conn.recv()
9        body = storage.read(req.path)  # no cache layer
10        conn.send(http.ok(body))
11        conn.close()

1# Set by physics, not by how busy the origin is.
2# Cross-ocean ~150 ms, cross-continent ~80 ms,
3# nearby ~30 ms (HPBN, ch. 1).
4def rtt_to(user_region):
5    distance_km = great_circle(user_region, ORIGIN)
6    propagation = distance_km / SPEED_OF_LIGHT_IN_FIBER
7    return 2 * propagation  # there AND back
8 
9# Notice: user_count does not appear anywhere here.
10# Adding users cannot shrink any one user's trip.