I think of it as a trigger, like in a database. By now we are having unconditional triggers; but I think lambdas plus some kind of status/context/finite_state_

I think of it as a trigger, like in a database. By now we are having unconditional triggers; but I think lambdas plus some kind of status/context/finite_state_machine could make some interesting piece of software not just for web services. Also transaction isolation would be great. I mean, enter a lambda make some calls to whatever service and if everything is OK, commit all those changes. If something goes wrong, do an automatic rollback. That would have a huge impact on lambda usage since you are not leaving half-done stuff.