anchor.diff:  stale shard copy.
   
   [float]
  -=== Make index creation resilient to index closing and full cluster crashes (STATUS: ONGOING, v5.0.0)
  +=== Make index creation resilient to index closing and full cluster crashes (STATUS: UNRELEASED, v5.0.0)
   
   Recovering an index requires a quorum (with an exception for 2) of shard copies to be available to allocate a primary. This means that
   a primary cannot be assigned if the cluster dies before enough shards have been allocated ({GIT}9126[#9126]). The same happens if an index
  
positive.code: 
  Other safeguards are tracked in the meta-issue {GIT}11511[#11511].
  
  [float]
  === Loss of documents during network partition (STATUS: ONGOING)
  
  If a network partition separates a node from the master, there is some window of time before the node detects it. The length of the window is dependent on the type of the partition. This window is extremely small if a socket is broken. More adversarial partitions, for example, silently dropping requests without breaking the socket can take longer (up to 3x30s using current defaults).
  
  
negative.code: To prevent this situation, the primary needs to wait for the master to acknowledge replica shard failures before acknowledging the write to the client. {GIT}14252[#14252]
  
  [float]
  === Safe primary relocations (STATUS: UNRELEASED, v5.0.0)
  
  When primary relocation completes, a cluster state is propagated that deactivates the old primary and marks the new primary as active. As
  cluster state changes are not applied synchronously on all nodes, there can be a time interval where the relocation target has processed the
  