First, tens of thousands of connections per second boils down to orders of magnitude fewer logins. In a typical modern web app, plenty of entire sessions are completed off a stored session token and never touch the login code.<p>Second, plenty of apps that are far bigger than yours have scaled bcrypt without event. 37signals is a public example. Other larger apps are using it without talking about it.<p>Third, in the <i>spectacularly unlikely</i> event that <i>password hashing</i> became a scalability obstacle, it's pure compute and scales horizontally without a problem. Note: I've never heard of someone having to do this.<p>Finally, the whole point of bcrypt is that it's tuneable. You dial it up to your pain threshold, and in the process cripple brute force attackers.