Zeitwerk is an efficient and thread-safe code loader for Ruby.

Given a conventional file structure, Zeitwerk is able to load your project's
classes and modules on demand (autoloading), or upfront (eager loading). You
don't need to write require calls for your own files, rather, you can streamline
your programming knowing that your classes and modules are available everywhere.
This feature is efficient, thread-safe, and matches Ruby's semantics for
constants.

Zeitwerk is also able to reload code, which may be handy while developing web
applications. Coordination is needed to reload in a thread-safe manner. The
documentation below explains how to do this.

The gem is designed so that any project, gem dependency, application, etc. can
have their own independent loader, coexisting in the same process, managing
their own project trees, and independent of each other. Each loader has its own
configuration, inflector, and optional logger.

Internally, Zeitwerk issues require calls exclusively using absolute file names,
so there are no costly file system lookups in $LOAD_PATH. Technically, the
directories managed by Zeitwerk do not even need to be in $LOAD_PATH.
Furthermore, Zeitwerk does only one single scan of the project tree, and it
descends into subdirectories lazily, only if their namespaces are used.