Change Etcd example to simpler component

Currently, all the examples use `etcd` which is quite complicated. We should be using something much simpler for clarity (although we could include `etcd` as well).

Review the repository examples that currently use etcd and determine what simpler component would make them clearer. Confirm the replacement and whether etcd should remain as an additional example; done means the examples consistently use the agreed simpler component and the resulting documentation is clear.

Written by the indexing model from the issue text.