RPC services can be messy to implement. It can be even messier if you go with microservices. Rather than writing a monolithic piece of software that’s simple to deploy but hard to maintain, you write many small services each dedicated to a specific functionality, with a clean scope of features. They can be running in different environments, written at different times, and managed by different teams. They can be as far as a remote service across the continent, or as close as a logical component living in your own server process providing its work through an interface, synchronous or asynchronous. All said, you want to put together the work of many smaller components to process your request.
This was exactly the problem that Blender, one of the major components of the Twitter Search backend, was facing. As one of the most complicated services in Twitter, it makes more than 30 calls to different services with complex interdependencies for a typical search request, eventually reaching hundreds of machines in the data center darkness.
Read more at the Twitter Blog
