Let's say memcache is down and the sessions backend doesn't work. In this case an empty reservation confirmation can be be shown which may be clicked away, but which does nothing. The reservation will look like it was confirmed, but it is not in the backend.
There should be more checks to ensure that the confirmation works like a transaction and either ends with success if everything worked or shows an error if anything was fishy.
Let's say memcache is down and the sessions backend doesn't work. In this case an empty reservation confirmation can be be shown which may be clicked away, but which does nothing. The reservation will look like it was confirmed, but it is not in the backend.
There should be more checks to ensure that the confirmation works like a transaction and either ends with success if everything worked or shows an error if anything was fishy.