The i18n system loads properties files from disk only. This happens on demand when they are needed the first time. During this load procedure, the I18nManager solves all the relative and absolute references and then keeps this translations in a in-memory cache.

When modifying translations using the translation tool, the cache is updated automatically with the new version of the translation.

The cache can be disable in the I18nModule for development purposes, however this will slow down the entire system. Even in a development environment I recommend not to disable the translation cache. Instead, when modifying a properties file directly on the file system you can press the "Empty cache" button from the administration menu where you also start the translation and language customizing tool. This will flush the entire cache and start rebuilding.