The Amazon Load Balancer only performs load balancing... a reverse proxy can be used for a whole lot of other scenarios... here are just a few... Rolling Upgra

The Amazon Load Balancer only performs load balancing... a reverse proxy can be used for a whole lot of other scenarios... here are just a few... Rolling Upgrades: you have 20 instances of V1 of your app, you want to slowly test them out, so you start with moving 5 instance to V2, then 5 more, etc. To switch from V1 to V2 gradually to make sure there are no major snags. Versioning: Make a single API available at the address http://foo.com/V1 http://foo.com/V1 and http://foo.com/V2 http://foo.com/V2 but those actually go to two different servers running two different applications. Sub domain to path rewrite: You want to provide customers with sub-domains at <customer>.foo.com but it actually serves up contents from service.foo.com/<customer> on the back-end. Virtual Sites on single server: Some providers (i.e. some shared services) only allow you to have one or just a few domains/sub-domains for a single instance of your application. Now you can have http://foo.com http://foo.com and http://bar.com http://bar.com actually host up pages from http://foobar.com/ http://foobar.com/ and the original requested address will be in a new HTTP header so your app at http://foobar.com/ http://foobar.com/ can distinguish the two. Instance Allocation per customer: Some multi-tenant architectures have a "home" node for each customer. In this case you could setup a rule that states that customer a.foo.com goes to instance x while customer b.foo.com goes to instance y.