Guidelines:

Should include

• What state does a router track? E.g. the participant list, whether each participant is read-only
• What are the different commit paths? E.g. read-only, single-write-shard, multi-write-shard
• What is the procedure for a two-phase commit? E.g. router forwards participant list to coordinator, coordinator makes participant list durable, etc

Code references

• TransactionRouter class
• TransactionCoordinatorService class
• TransactionCoordinator class