One of the NextGen requirements is some degree of recovery from remote service failure, such as a (temporarily) unavailable product database.
Access to product information is the first case used to explore the recovery and failover design strategy. Afterwards, access to the accounting service is explored, which has a slightly different solution.
To review part of the technical memo:
Technical MemoIssue: Reliability—Recovery from Remote Service Failure
Solution Summary: Location transparency using service lookup, failover from remote to local, and local service partial replication.