> Most systems aren't really at the scale where the BEAM really excels.
BEAM's concurrency model can be helpful even at small scale. Eg, suppose you have a web app where requests to one endpoint are computationally expensive (by design, or only for certain input, or because there's a bug). If you use (eg) Rails with Unicorn, you have a smallish, fixed number of processes available to serve requests. If N is 10 and you get 10 requests to that endpoint, every other request to your site is now standing in line, waiting to be served.
By contrast, Cowboy (the web server a Phoenix app would use) will spawn a new, tiny BEAM process per incoming request, and each process gets to run a fixed number of instructions before it is paused by the scheduler and goes back to the end of the line. So even on a single-core system, a few expensive requests wouldn't affect typical requests noticeably, and the effect would be gradually increasing latency as you got larger numbers of expensive requests, not a sudden and dramatic spike.
Maybe this won't matter for your site, but it's something that you don't have to worry about.
BEAM's concurrency model can be helpful even at small scale. Eg, suppose you have a web app where requests to one endpoint are computationally expensive (by design, or only for certain input, or because there's a bug). If you use (eg) Rails with Unicorn, you have a smallish, fixed number of processes available to serve requests. If N is 10 and you get 10 requests to that endpoint, every other request to your site is now standing in line, waiting to be served.
By contrast, Cowboy (the web server a Phoenix app would use) will spawn a new, tiny BEAM process per incoming request, and each process gets to run a fixed number of instructions before it is paused by the scheduler and goes back to the end of the line. So even on a single-core system, a few expensive requests wouldn't affect typical requests noticeably, and the effect would be gradually increasing latency as you got larger numbers of expensive requests, not a sudden and dramatic spike.
Maybe this won't matter for your site, but it's something that you don't have to worry about.