Developers are now deploying Rails and Sinatra applications to Google App Engine. These apps run in a servlet container, with access to all the Java APIs. Unlike a traditional Ruby hosting environment, new app instances spin-up on-demand, so developers avoid paying for servers that sit idle. Unfortunately, new Rails instances can take many seconds to spin-up. Dubious provides a way to bypass the spin-up problem by replacing part (or all) of your app with Mirah code, which can be almost identical to the Ruby code found in a Rails app. Using Dubious, each new instance can spin-up in about a second, with scalability and performance that beats all other traditional web frameworks. This is possible because Mirah uses compile-time macros and plugins to generate code, instead using abstractions that create runtime dependencies with associated initialization costs.