Perlbal is a single-threaded event-based server supporting HTTP load balancing, web serving, and a mix of the two. Perlbal can act as either a web server or a reverse proxy.

One of the defining things about Perlbal is that almost everything can be configured or reconfigured on the fly without needing to restart the software. A basic configuration file containing a management port enables you to easily perform operations on a running instance of Perlbal.

Perlbal can also be extended by means of per-service (and global) plugins that can override many parts of request handling and behavior.