gistfile1.txt

First up: 3.5 MB of postdata where the properties all end up in the same hash bucket

einaros@dumpster:~/crashtest$ time curl -d @postdata_bucketcrash http://localhost:9999
279343: ok

real	0m52.142s
user	0m0.044s
sys	0m0.052s

Second: 3.5 MB of postdata where the properties (mostly) end up in different hash buckets

einaros@dumpster:~/crashtest$ time curl -d @postdata_plain http://localhost:9999
279343: ok

real	0m1.562s
user	0m0.028s
sys	0m0.052s

Conclusion:

For this test, with a relatively small amount of data, parsing the colliding properties takes roughly 33x the time. Generating a significantly larger data set is trivial => keeping a server busy is trivial.

The test application:

var express = require('express');
var app = express.createServer();
app.use(express.bodyParser());
app.listen(9999);
app.post('/', function(req, res) {
  res.end(Object.keys(req.body).length + ': ok\n');
});