anchor.diff:    delta carried in that entry. This information is used to summarize transaction
     metadata when this entry is snapshotted.
   
  -=== Internal state persistence
  +==== Internal state persistence
     The Backend creates a hierarchy of actors to track interactions with the Frontend.
     Information necessary to recreate these actors needs to be persisted within
     the journal. This boils down to existence of Local Histories and the last
  
positive.code:   with FrontendIdentifier, it also uniquely identifies any transaction that has
    ever executed in the cluster, e.g. forming a GlobalTransactionIdentifier.
  
  == Frontend persistence
    As noted above, implementation of the Frontend Generation requires each member
    to persistently store a single 64 bit counter. To keep the persistence interfaces
    within a member consistent, Frontend uses Akka Persistence to maintain this
  
negative.code:   by the application and enough metadata about Local Histories and Transactions
    to make state recovery across shard leadership movement possible.
  
  ==== User Data persistence
    The Snapshot needs to identify all transactions which have been integrated
    into it. Enumerating all of them is clearly not practical, hence we exploit
    the monotonic nature of identifiers' relationship to Global History. For each
  