The YAZ Proxy is highly configurable and can be used in a number of different applications, ranging from debugging Z39.50-based applications and protecting overworked servers, to improving the performance of stateless WWW/Z39.50 gateways. Among other features, it includes:
Load balancing across multiple backend servers
Session-sharing and pre-initialization to improve performance in servers with expensive session initialization
Configurable request filtering, to keep bad requests from reaching the server
Load governor function limits requests from aggressive batch-mode clients
Efficient multiplexing software enables small memory footprint and very high performance
Z39.50 character set negotiation support.
The proxy application and the proxy library is covered by the GPL.