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    <p>Your understanding of exec is roughly correct, my concern is that you are using it when you do not need to do so... In your question you only mention I/O types of oeprations, which node handles very efficiently within it's single threaded event model of doing things. Despite being single threaded, the event model allows code to run without blocking the main event loop(unless you're doing VERY CPU intensive operations..., of which Database requests, and file processing are not included) That being said, you should not need to launch an additional dyno to do what you want.</p> <p>Think of a dyno as a single processor computer. Whatever you can do on a machine that has a single processor you can do on your dyno, with no extra charges or created dynos. Though, a dyno does have considerably less memory than a single core processor computer could take advantage of. So, any subprocesses you wish to spawn do not need another dyno to run on. Every master process you wish to run, will need its own dyno.</p> <pre><code>var http = require('http'); http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('An amount of data that will take 1 second to send');//This will not block the event loop }).listen(1337, '127.0.0.1'); var http = require('http'); http.createServer(function (req, res) { while(true) { break after 1 second; //this will block the event loop for 1 second } res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello World\n'); }).listen(1337, '127.0.0.1'); </code></pre> <p>Consider the two servers in the code above. Both servers have roughly one second of work to do. The first example can service thousands of requests per second, the second example only 1. Sending data, database requests, server requests, file IO, etc... all would behave as the first example... very few things in Node behave like the second example. If you have something that fits under the second example, you are likely better off picking a different language, than trying to force node to work for a use case it is very poorly designed for.</p>
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    1. COOh, ok. So it seems I was mistaking single process with single thread..? Do you know if there is a limit to the amount of processes I can run on one dyno?
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    2. COI would like to strongly discourage you from launching an abundance of processes. If you believe that your node process requires the launching of more than 1 or 2 workers for a processor, you are likely not using node correctly, or your use case would be better suited for a different programming language. I will write a little demo code for you. That being said, the number is likely limited only by whatever operating system heroku is using, not on any limitations they wish to place upon you.
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    3. COThus your true limitation, is likely RAM. Dynos can support 512MB of ram(last I checked, which was a while ago). When you fork a process, the memory from that process comes with you, copied over into it's own environment. So assuming a 100MB process, you could spawn 5 such processes. (The math here isn't quite exact, this is just an overview, benchmarking might be in order)
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