https://github.com/elastic/elasticsearch/pull/97304 removes several places that might do an expensive rebuild of the cluster state via `getStateForMasterService`. There's one other call we should be able to remove, in `JoinValidationService`, but it's a little tricky since we rely on seeing the last-accepted state for the cluster UUID validation, and it's not obviously ok to expose the last-accepted state without the no-master block.

This is a fairly minor issue because we do not do this join validation during elections, only if we're the elected master, and in that case `getStateForMasterService` is cheap. But that's not guaranteed, and we should strengthen this to avoid the that expensive step whenever possible.
server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java
}
            }
            becomeCandidate("onLeaderFailure");
        }
    }
    private void removeNode(DiscoveryNode discoveryNode, String reason) {
        synchronized (mutex) {
            if (mode == Mode.LEADER) {
                var task = new NodeLeftExecutor.Task(discoveryNode, reason, () -> joinReasonService.onNodeRemoved(discoveryNode, reason));
                nodeLeftQueue.submitTask("node-left", task, null);
            }
        }
    }
    void onFollowerCheckRequest(FollowerCheckRequest followerCheckRequest) {
        synchronized (mutex) {
            ensureTermAtLeast(followerCheckRequest.getSender(), followerCheckRequest.getTerm());
            if (getCurrentTerm() != followerCheckRequest.getTerm()) {
                logger.trace("onFollowerCheckRequest: current term is [{}], rejecting {}", getCurrentTerm(), followerCheckRequest);
                throw new CoordinationStateRejectedException(
                    "onFollowerCheckRequest: current term is [" + getCurrentTerm() + "], rejecting " + followerCheckRequest
                );
            }
            
            
            
            
            if (getLastAcceptedState().term() < getCurrentTerm()) {
                becomeFollower("onFollowerCheckRequest", followerCheckRequest.getSender());
            } else if (mode == Mode.FOLLOWER) {
                logger.trace("onFollowerCheckRequest: responding successfully to {}", followerCheckRequest);