What do you do when you want the benefits of modularity and abstraction during development, but you aren't willing to subject users with any runtime overhead to get it? If you're the GWT team, you invent deferred binding. Deferred binding is a pluggable compile-time type substitution and code generation mechanism. This unique approach to program modularization provides many of the benefits of Java reflection and dynamic class loading without compromising the GWT compiler's ability to optimize the heck out of your code. The GWT libraries leverage deferred binding to provide zero-overhead browser abstractions, highly optimizable internationalization, automatic image bundling, and high-performance, polymorphic RPC. Best of all, deferred binding is extensible, and this session will show you how you can take advantage of it to build powerful, reusable and, most importantly, efficient abstractions in your own libraries.