# APIs: Load Balancing & Redundancy

_(c) AMWA 2018, CC Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0)_

## System API

* An HTTP load balancing proxy (such as HAProxy) may be inserted in front of multiple System API instances which share common data. In this instance the proxy is the entity advertised via DNS-SD (rather than individual System APIs).
* Multiple System APIs may exist as separate entities in a network, but with a common data set. Each API should be advertised via a separate DNS-SD record. Priorities may be defined for each of these APIs to determine an order of precedence for their usage by clients.
* An HTTP cache layer may be used in front of a System API instance to reduce the load on the system provided this cache is invalidated when resources held in the registry are changed.
