Faster Ruby: Thoughts from the outside
&gt; What kind of speedup is available for big Rails applications? If 90% of the time in an application is spent in database calls, then there’s little opportunity for improvement via JIT technologies.<p>This is written as speculation of course, but it matches some long-time &quot;conventional wisdom&quot;, that most Rails apps spend most of their time on I&#x2F;O waiting for something external.<p>That may have been true once, but i don&#x27;t believe it&#x27;s true anymore.<p>My Rails apps now, when things like &quot;n+1 database query problems&quot; are properly eliminated, all spend more of their time on CPU than I&#x2F;O, 60-80%. (I think most of that CPU time is ActionView rendering. Unsure about CPU parts of ActiveRecord, that aren&#x27;t waiting on DB, but converting db results to in-memory AR objects etc).<p>When this comes up and I ask around on social media who else has actually looked at their app and can confirm or deny, almost all who respond agree. I would be curious to see here too.<p>Definitely some more systematic rather than anecdotal investigation is called for. But I think it&#x27;s time to stop repeating that it&#x27;s likely that a Rails app is I&#x2F;O-bound rather than CPU-bound, my experience leads me to think the reverse is currently likely.<p>[*edit* after I wrote this comment, I noticed <i>multiple</i> other comments in this thread saying basically the same thing. OK, so. Can we put this rumor to rest?]