Read-After-Write Consistency
Summary: A guarantee that if a user reloads the page, they will always see any updates they submitted themselves. It makes no promises about other users.
Sources: chapter5
Last updated: 2026-04-15
Read-after-write consistency (also known as read-your-writes consistency) is a guarantee that if the user submits some data, they will always see that data when they look at it later. It reassures the user that their own input has been saved correctly (source: chapter5, p. 163).
Implementation Techniques
- Read from the leader: When reading something that the user might have modified, read it from the leader. For example, a user’s own profile should always be read from the leader, while other users’ profiles can be read from followers (source: chapter5, p. 163).
- Time-based routing: The client can remember the timestamp of its most recent write. The system then ensures that the replica serving a read for that user reflects updates at least until that timestamp (source: chapter5, p. 163).
- Cross-device consistency: If a user accesses the service from multiple devices (e.g., a desktop and a phone), the system should provide a consistent view across all of them (source: chapter5, p. 164).