Potential template:

The sharding vector clock (config OpTime, logical clock, databaseVersion, collectionVersion, shardVersion)

• Should include
  • What is the type of each of these versions
  • How is each version derived (e.g., shardVersion is the max across all chunks owned by the shard, etc)
  • What are the processes, at a high level, which advance each version (e.g. writes to the config server advance the config OpTime)
  • At a conceptual level, how are config OpTime and logical time gossiped?
  • Why is there a config OpTime separate from clusterTime?
• Code references
  • Where config OpTime is attached in requests and responses
  • Where config OpTime is stored in memory on each node
  • Where clusterTime is attached in requests and responses
  • Where clusterTime is stored in memory on each node
  • An example of where shardVersion and databaseVersion are attached in egress requests and parsed in ingress requests
  • Where collectionVersion is used to do an incremental refresh