Response flag. All server responses include flags field, and server sets a flag when the assignment has changed since the last response. It is up to the client to retrieve updated assignment when needed. This mechanism is used in Ignite 2.x.
Pros: Low overhead, no extra network traffic.
Cons: Idle clients do not get Unlike Ignite 2.x, there is no concept of TopologyVersion in Ignite 3. So when there are multiple server connections, a notification for the same assignment update will come from all of them, and it is not possible to tell whether it was the same update or a new one. This may cause unnecessary assignment update requests. A workaround is to use only one connection to track assignment changes. Even if there is no activity on this connection, heartbeats (IEP-83) will trigger the update.
Server → client notification. As soon as assignment changes, server sends a message to all clients.
Pros: Immediate update for all clients.
Cons: Increased network traffic and server load. Some clients may not need the update at all (not all APIs require this).
PrimaryReplicaMissException (suggested in
Jira
server ASF JIRA
serverId 5aa69414-a9e9-3523-82ec-879b028fb15b
key IGNITE-17394
comments).
Pros: No protocol changes.
Cons: Retry is required on replica miss (complicated & inefficient). Using exceptions for control flow.

The first approach (response flag) is battle tested and seems to be the most optimal.

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