Rails recently introduced Global IDs. It’s a very simple but potentially very powerful concept, and one I haven’t come across before.

The format is:


i.e. a combination of an app, a type, and an ID. e.g. “Twitter User 114”; “Epicurious Recipe 8421”. It’s a nice lightweight way to standardise URL schemes without trying to go full-HATEOAS. A typically Rails approach to pragmatic conventions.

A good example of using it is for pushing GIDs to queueing systems. When they are later retrieved from the message store, it will be unambiguous about how to fetch that record, and that’s exactly how the new ActiveJob works in Rails 4.2. It supports a notion of an app-specific locator, so the queuing system doesn’t have to assume all records are in MySQL or Mongo or whatever. The app tells it how to retrieve a certain kind of record with a specific ID.