A Crash Course in Analyzing Memory Usage in Ruby

The app handles a number of legacy URL paths, and redirects each one to a configurable location. This is implemented as a custom middleware. When the app boots we load the YAML configuration, which maps from legacy paths to new paths, into a hash (both keys and values are strings). When a request arrives, we look up the path in the hash, if an entry exists, return a 301 (Moved Permanently) with a Location of the new path. Otherwise the request is passed on to the app. Initially there were a few hundred redirects and everything worked great. Then we learned that rather than a few hundred mappings we needed to handle many thousands.